[cloud_firestore]: Add to app support

### Is there an existing issue for this?

- [X] I have searched the existing issues.

### Which plugins are affected?

Database

### Which platforms are affected?

iOS

### Description

I'm migrating an existing iOS app into flutter using [add to app](https://docs.flutter.dev/add-to-app). The idea of add_to_app is that you can progressively migrate or provide certain features of the app with flutter.

For my app I'm trying migrate a screen that is not loaded during app initialization, so my flutter main() code is not executed on startup. This means that I perform certain queries with the native iOS Firestore SDK before I actually use flutter.

Now, when I start my flutter screen, I initialize firebase as usual, but when I try to make a query, I have an issue because the cloud firestore plugin tries to initialize firestore as well, this causes an issue because it tries to set the firestore settings after I have already performed queries with the native SDK

https://github.com/firebase/flutterfire/blob/a4be69731d41aade5dfcfb154af3292551633874/packages/cloud_firestore/cloud_firestore/ios/Classes/FLTFirebaseFirestorePlugin.m#L227-L253

I know it's not a common scenario, but I would expect the firestore database to support add_to_app. I'm not sure if there could be a way to somehow bypass this or you could implement a feature/fix.

### Reproducing the issue

Steps to reproduce:

- Clone an add_to_app project from one of the [examples](https://github.com/flutter/samples/tree/main/add_to_app/fullscreen/ios_fullscreen).
- Add cloud_firestore plugin.
- In the iOS code, make a firestore query on the view controller before flutter is presented.
- Add another firestore query on the flutter code
- Run the app, verify that the native query is executed. then click on the button to show the flutter screen.

Expected result:
Flutter code should perform firestore query

Actual result:
Error is thrown, firestore settings should only be set on startup

it works fine if I remove this line

https://github.com/firebase/flutterfire/blob/a4be69731d41aade5dfcfb154af3292551633874/packages/cloud_firestore/cloud_firestore/ios/Classes/FLTFirebaseFirestorePlugin.m#L253

### Firebase Core version

3.6.0

### Flutter Version

3.24.2

### Relevant Log Output

```shell
Terminating app due to uncaught exception 'FIRIllegalStateException', reason: 'Firestore instance has already been started and its settings can no longer be changed. You can only set settings before calling any other methods on a Firestore instance.
```

### Flutter dependencies

Expand Flutter dependencies snippet

```yaml

dependencies:
- another_flushbar 1.12.30 [flutter]
- app_settings 5.1.1 [flutter plugin_platform_interface]
- audio_session 0.1.21 [flutter flutter_web_plugins rxdart meta]
- cached_network_image 3.4.1 [cached_network_image_platform_interface cached_network_image_web flutter flutter_cache_manager octo_image]
- chewie 1.8.5 [cupertino_icons flutter provider video_player wakelock_plus]
- cloud_firestore 5.4.4 [cloud_firestore_platform_interface cloud_firestore_web collection firebase_core firebase_core_platform_interface flutter meta]
- cloud_functions 5.1.3 [cloud_functions_platform_interface cloud_functions_web firebase_core firebase_core_platform_interface flutter]
- collection 1.18.0
- connectivity_plus 6.1.0 [flutter flutter_web_plugins connectivity_plus_platform_interface web meta nm collection]
- dartz 0.10.1
- dio 5.7.0 [async http_parser meta path dio_web_adapter]
- equatable 2.0.5 [collection meta]
- firebase_auth 5.3.1 [firebase_auth_platform_interface firebase_auth_web firebase_core firebase_core_platform_interface flutter meta]
- firebase_core 3.6.0 [firebase_core_platform_interface firebase_core_web flutter meta]
- firebase_database 11.1.4 [firebase_core firebase_core_platform_interface firebase_database_platform_interface firebase_database_web flutter]
- firebase_messaging 15.1.3 [firebase_core firebase_core_platform_interface firebase_messaging_platform_interface firebase_messaging_web flutter meta]
- firebase_storage 12.3.4 [firebase_core firebase_core_platform_interface firebase_storage_platform_interface firebase_storage_web flutter]
- flutter 0.0.0 [characters collection material_color_utilities meta vector_math sky_engine]
- flutter_bloc 8.1.6 [bloc flutter provider]
- flutter_chat_ui 1.6.15 [diffutil_dart equatable flutter flutter_chat_types flutter_link_previewer flutter_parsed_text intl meta photo_view scroll_to_index url_launcher visibility_detector]
- flutter_localizations 0.0.0 [flutter intl characters clock collection material_color_utilities meta path vector_math]
- flutter_sound 9.16.3 [path_provider recase uuid provider path synchronized logger flutter flutter_sound_platform_interface flutter_sound_web]
- flutter_svg 2.0.11 [flutter http vector_graphics vector_graphics_codec vector_graphics_compiler]
- freezed_annotation 2.4.4 [collection json_annotation meta]
- get_it 8.0.2 [async collection meta]
- go_router 14.3.0 [collection flutter flutter_web_plugins logging meta]
- image_picker 1.1.2 [flutter image_picker_android image_picker_for_web image_picker_ios image_picker_linux image_picker_macos image_picker_platform_interface image_picker_windows]
- injectable 2.5.0 [get_it meta]
- intl 0.19.0 [clock meta path]
- json_annotation 4.9.0 [meta]
- logging 1.3.0
- path_provider 2.1.5 [flutter path_provider_android path_provider_foundation path_provider_linux path_provider_platform_interface path_provider_windows]
- permission_handler 11.3.1 [flutter meta permission_handler_android permission_handler_apple permission_handler_html permission_handler_windows permission_handler_platform_interface]
- retry 3.1.2
- rxdart 0.28.0
- sentry_flutter 8.9.0 [flutter flutter_web_plugins sentry package_info_plus meta ffi file]
- shared_preferences 2.3.2 [flutter shared_preferences_android shared_preferences_foundation shared_preferences_linux shared_preferences_platform_interface shared_preferences_web shared_preferences_windows]
- shimmer 3.0.0 [flutter]
- url_launcher 6.3.1 [flutter url_launcher_android url_launcher_ios url_launcher_linux url_launcher_macos url_launcher_platform_interface url_launcher_web url_launcher_windows]
- webview_flutter 4.10.0 [flutter webview_flutter_android webview_flutter_platform_interface webview_flutter_wkwebview]

dev dependencies:
- build_runner 2.4.13 [analyzer args async build build_config build_daemon build_resolvers build_runner_core code_builder collection crypto dart_style frontend_server_client glob graphs http_multi_server io js logging meta mime package_config path pool pub_semver pubspec_parse shelf shelf_web_socket stack_trace stream_transform timing watcher web_socket_channel yaml]
- cloud_firestore_odm_generator 1.0.0-dev.89 [analyzer build build_config cloud_firestore_odm collection freezed_annotation graphs json_annotation meta recase source_gen source_helper]
- flutter_lints 5.0.0 [lints]
- flutter_test 0.0.0 [flutter test_api matcher path fake_async clock stack_trace vector_math leak_tracker_flutter_testing async boolean_selector characters collection leak_tracker leak_tracker_testing material_color_utilities meta source_span stream_channel string_scanner term_glyph vm_service]
- freezed 2.5.7 [analyzer build build_config collection meta source_gen freezed_annotation json_annotation dart_style]
- injectable_generator 2.6.2 [build source_gen path glob analyzer code_builder dart_style injectable collection recase meta]
- json_serializable 6.8.0 [analyzer async build build_config collection json_annotation meta path pub_semver pubspec_parse source_gen source_helper]

transitive dependencies:
- _fe_analyzer_shared 72.0.0 [meta]
- _flutterfire_internals 1.3.44 [collection firebase_core firebase_core_platform_interface flutter meta]
- _macros 0.3.2
- analyzer 6.7.0 [_fe_analyzer_shared collection convert crypto glob macros meta package_config path pub_semver source_span watcher yaml]
- args 2.6.0
- async 2.11.0 [collection meta]
- bloc 8.1.4 [meta]
- boolean_selector 2.1.1 [source_span string_scanner]
- build 2.4.1 [analyzer async convert crypto glob logging meta package_config path]
- build_config 1.1.1 [checked_yaml json_annotation path pubspec_parse yaml]
- build_daemon 4.0.2 [built_collection built_value crypto http_multi_server logging path pool shelf shelf_web_socket stream_transform watcher web_socket_channel]
- build_resolvers 2.4.2 [analyzer async build collection convert crypto graphs logging package_config path pool pub_semver stream_transform yaml]
- build_runner_core 7.3.2 [async build build_config build_resolvers collection convert crypto glob graphs json_annotation logging meta package_config path pool timing watcher yaml]
- built_collection 5.1.1
- built_value 8.9.2 [built_collection collection fixnum meta]
- cached_network_image_platform_interface 4.1.1 [flutter flutter_cache_manager]
- cached_network_image_web 1.3.1 [cached_network_image_platform_interface flutter flutter_cache_manager web]
- characters 1.3.0
- checked_yaml 2.0.3 [json_annotation source_span yaml]
- clock 1.1.1
- cloud_firestore_odm 1.0.0-dev.88 [cloud_firestore flutter json_annotation meta]
- cloud_firestore_platform_interface 6.4.3 [_flutterfire_internals collection firebase_core flutter meta plugin_platform_interface]
- cloud_firestore_web 4.3.2 [_flutterfire_internals cloud_firestore_platform_interface collection firebase_core firebase_core_web flutter flutter_web_plugins]
- cloud_functions_platform_interface 5.5.37 [firebase_core flutter meta plugin_platform_interface]
- cloud_functions_web 4.10.2 [cloud_functions_platform_interface firebase_core firebase_core_web flutter flutter_web_plugins]
- code_builder 4.10.1 [built_collection built_value collection matcher meta]
- connectivity_plus_platform_interface 2.0.1 [flutter meta plugin_platform_interface]
- convert 3.1.2 [typed_data]
- cross_file 0.3.4+2 [meta web]
- crypto 3.0.6 [typed_data]
- csslib 1.0.2 [source_span]
- cupertino_icons 1.0.8
- dart_style 2.3.7 [analyzer args collection package_config path pub_semver source_span]
- dbus 0.7.10 [args ffi meta xml]
- diffutil_dart 4.0.1
- dio_web_adapter 2.0.0 [dio http_parser meta web]
- fake_async 1.3.1 [clock collection]
- ffi 2.1.3
- file 7.0.1 [meta path]
- file_selector_linux 0.9.3 [cross_file file_selector_platform_interface flutter]
- file_selector_macos 0.9.4+2 [cross_file file_selector_platform_interface flutter]
- file_selector_platform_interface 2.6.2 [cross_file flutter http plugin_platform_interface]
- file_selector_windows 0.9.3+3 [cross_file file_selector_platform_interface flutter]
- firebase_auth_platform_interface 7.4.7 [_flutterfire_internals collection firebase_core flutter meta plugin_platform_interface]
- firebase_auth_web 5.13.2 [firebase_auth_platform_interface firebase_core firebase_core_web flutter flutter_web_plugins http_parser meta web]
- firebase_core_platform_interface 5.3.0 [collection flutter flutter_test meta plugin_platform_interface]
- firebase_core_web 2.18.1 [firebase_core_platform_interface flutter flutter_web_plugins meta web]
- firebase_database_platform_interface 0.2.5+44 [_flutterfire_internals collection firebase_core flutter meta plugin_platform_interface]
- firebase_database_web 0.2.6+2 [collection firebase_core firebase_core_web firebase_database_platform_interface flutter flutter_web_plugins]
- firebase_messaging_platform_interface 4.5.46 [_flutterfire_internals firebase_core flutter meta plugin_platform_interface]
- firebase_messaging_web 3.9.2 [_flutterfire_internals firebase_core firebase_core_web firebase_messaging_platform_interface flutter flutter_web_plugins meta web]
- firebase_storage_platform_interface 5.1.31 [_flutterfire_internals collection firebase_core flutter meta plugin_platform_interface]
- firebase_storage_web 3.10.3 [_flutterfire_internals async firebase_core firebase_core_web firebase_storage_platform_interface flutter flutter_web_plugins http meta web]
- fixnum 1.1.1
- flutter_cache_manager 3.4.1 [clock collection file flutter http path path_provider rxdart sqflite uuid]
- flutter_chat_types 3.6.2 [equatable json_annotation meta]
- flutter_link_previewer 3.2.2 [flutter flutter_chat_types flutter_linkify html http linkify meta url_launcher]
- flutter_linkify 6.0.0 [flutter linkify]
- flutter_parsed_text 2.2.1 [flutter]
- flutter_plugin_android_lifecycle 2.0.23 [flutter]
- flutter_sound_platform_interface 9.16.3 [flutter plugin_platform_interface logger]
- flutter_sound_web 9.16.3 [flutter_sound_platform_interface flutter logger flutter_web_plugins js web]
- flutter_web_plugins 0.0.0 [flutter characters collection material_color_utilities meta vector_math]
- frontend_server_client 4.0.0 [async path]
- glob 2.1.2 [async collection file path string_scanner]
- graphs 2.3.2 [collection]
- html 0.15.5 [csslib source_span]
- http 1.2.2 [async http_parser meta web]
- http_multi_server 3.2.1 [async]
- http_parser 4.0.2 [collection source_span string_scanner typed_data]
- image_picker_android 0.8.12+17 [flutter flutter_plugin_android_lifecycle image_picker_platform_interface]
- image_picker_for_web 3.0.6 [flutter flutter_web_plugins image_picker_platform_interface mime web]
- image_picker_ios 0.8.12+1 [flutter image_picker_platform_interface]
- image_picker_linux 0.2.1+1 [file_selector_linux file_selector_platform_interface flutter image_picker_platform_interface]
- image_picker_macos 0.2.1+1 [file_selector_macos file_selector_platform_interface flutter image_picker_platform_interface]
- image_picker_platform_interface 2.10.0 [cross_file flutter http plugin_platform_interface]
- image_picker_windows 0.2.1+1 [file_selector_platform_interface file_selector_windows flutter image_picker_platform_interface]
- io 1.0.4 [meta path string_scanner]
- js 0.7.1
- leak_tracker 10.0.5 [clock collection meta path vm_service]
- leak_tracker_flutter_testing 3.0.5 [flutter leak_tracker leak_tracker_testing matcher meta]
- leak_tracker_testing 3.0.1 [leak_tracker matcher meta]
- linkify 5.0.0
- lints 5.0.0
- logger 2.4.0
- macros 0.1.2-main.4 [_macros]
- matcher 0.12.16+1 [async meta stack_trace term_glyph test_api]
- material_color_utilities 0.11.1 [collection]
- meta 1.15.0
- mime 2.0.0
- nested 1.0.0 [flutter]
- nm 0.5.0 [dbus]
- octo_image 2.1.0 [flutter]
- package_config 2.1.0 [path]
- package_info_plus 8.1.0 [ffi flutter flutter_web_plugins http meta path package_info_plus_platform_interface web win32 clock]
- package_info_plus_platform_interface 3.0.1 [flutter meta plugin_platform_interface]
- path 1.9.0
- path_parsing 1.1.0 [meta vector_math]
- path_provider_android 2.2.12 [flutter path_provider_platform_interface]
- path_provider_foundation 2.4.0 [flutter path_provider_platform_interface]
- path_provider_linux 2.2.1 [ffi flutter path path_provider_platform_interface xdg_directories]
- path_provider_platform_interface 2.1.2 [flutter platform plugin_platform_interface]
- path_provider_windows 2.3.0 [ffi flutter path path_provider_platform_interface]
- permission_handler_android 12.0.13 [flutter permission_handler_platform_interface]
- permission_handler_apple 9.4.5 [flutter permission_handler_platform_interface]
- permission_handler_html 0.1.3+2 [flutter flutter_web_plugins permission_handler_platform_interface web]
- permission_handler_platform_interface 4.2.3 [flutter meta plugin_platform_interface]
- permission_handler_windows 0.2.1 [flutter permission_handler_platform_interface]
- petitparser 6.0.2 [meta]
- photo_view 0.15.0 [flutter]
- platform 3.1.6
- plugin_platform_interface 2.1.8 [meta]
- pool 1.5.1 [async stack_trace]
- provider 6.1.2 [collection flutter nested]
- pub_semver 2.1.4 [collection meta]
- pubspec_parse 1.3.0 [checked_yaml collection json_annotation pub_semver yaml]
- recase 4.1.0
- scroll_to_index 3.0.1 [flutter]
- sentry 8.9.0 [http meta stack_trace uuid]
- shared_preferences_android 2.3.3 [flutter shared_preferences_platform_interface]
- shared_preferences_foundation 2.5.3 [flutter shared_preferences_platform_interface]
- shared_preferences_linux 2.4.1 [file flutter path path_provider_linux path_provider_platform_interface shared_preferences_platform_interface]
- shared_preferences_platform_interface 2.4.1 [flutter plugin_platform_interface]
- shared_preferences_web 2.4.2 [flutter flutter_web_plugins shared_preferences_platform_interface web]
- shared_preferences_windows 2.4.1 [file flutter path path_provider_platform_interface path_provider_windows shared_preferences_platform_interface]
- shelf 1.4.1 [async collection http_parser path stack_trace stream_channel]
- shelf_web_socket 2.0.0 [shelf stream_channel web_socket_channel]
- sky_engine 0.0.99
- source_gen 1.5.0 [analyzer async build dart_style glob path source_span yaml]
- source_helper 1.3.4 [analyzer collection source_gen]
- source_span 1.10.0 [collection path term_glyph]
- sprintf 7.0.0
- sqflite 2.4.0 [flutter sqflite_android sqflite_darwin sqflite_platform_interface sqflite_common path]
- sqflite_android 2.4.0 [flutter sqflite_common path sqflite_platform_interface]
- sqflite_common 2.5.4+5 [synchronized path meta]
- sqflite_darwin 2.4.1-1 [flutter sqflite_platform_interface meta sqflite_common path]
- sqflite_platform_interface 2.4.0 [flutter platform sqflite_common plugin_platform_interface meta]
- stack_trace 1.11.1 [path]
- stream_channel 2.1.2 [async]
- stream_transform 2.1.0
- string_scanner 1.2.0 [source_span]
- synchronized 3.3.0+3
- term_glyph 1.2.1
- test_api 0.7.2 [async boolean_selector collection meta source_span stack_trace stream_channel string_scanner term_glyph]
- timing 1.0.1 [json_annotation]
- typed_data 1.4.0 [collection]
- url_launcher_android 6.3.14 [flutter url_launcher_platform_interface]
- url_launcher_ios 6.3.1 [flutter url_launcher_platform_interface]
- url_launcher_linux 3.2.0 [flutter url_launcher_platform_interface]
- url_launcher_macos 3.2.1 [flutter url_launcher_platform_interface]
- url_launcher_platform_interface 2.3.2 [flutter plugin_platform_interface]
- url_launcher_web 2.3.3 [flutter flutter_web_plugins url_launcher_platform_interface web]
- url_launcher_windows 3.1.3 [flutter url_launcher_platform_interface]
- uuid 4.5.1 [crypto sprintf meta fixnum]
- vector_graphics 1.1.12 [flutter http vector_graphics_codec]
- vector_graphics_codec 1.1.12
- vector_graphics_compiler 1.1.12 [args meta path path_parsing vector_graphics_codec xml]
- vector_math 2.1.4
- video_player 2.9.2 [flutter html video_player_android video_player_avfoundation video_player_platform_interface video_player_web]
- video_player_android 2.7.16 [flutter video_player_platform_interface]
- video_player_avfoundation 2.6.2 [flutter video_player_platform_interface]
- video_player_platform_interface 6.2.3 [flutter plugin_platform_interface]
- video_player_web 2.3.3 [flutter flutter_web_plugins video_player_platform_interface web]
- visibility_detector 0.4.0+2 [flutter]
- vm_service 14.2.5
- wakelock_plus 1.2.8 [flutter flutter_web_plugins meta wakelock_plus_platform_interface win32 dbus package_info_plus web]
- wakelock_plus_platform_interface 1.2.1 [flutter plugin_platform_interface meta]
- watcher 1.1.0 [async path]
- web 1.1.0
- web_socket 0.1.6 [web]
- web_socket_channel 3.0.1 [async crypto stream_channel web web_socket]
- webview_flutter_android 4.0.0 [flutter webview_flutter_platform_interface]
- webview_flutter_platform_interface 2.10.0 [flutter meta plugin_platform_interface]
- webview_flutter_wkwebview 3.16.0 [flutter path webview_flutter_platform_interface]
- win32 5.7.2 [ffi]
- xdg_directories 1.1.0 [meta path]
- xml 6.5.0 [collection meta petitparser]
- yaml 3.1.2 [collection source_span string_scanner]

```

### Additional context and comments

Thought this is a bug, maybe it doesn't really need to be fixed, I'm open to suggestions on how to bypass this issue, maybe we call on AppDelegate

i.e
```swift
[FLTFirebaseFirestoreUtils setCachedFIRFirestoreInstance:firestore
forAppName:app.name
databaseURL:databaseUrl];
```

though I'm not sure if FLTFirebaseFirestoreUtils is public