Tracking issue for add-to-app

There are some things that need to be done in Android Studio to support add-to-app. Some of these may be applicable to IntelliJ.
- **Phase 1**
- [x] Update the new project wizard to allow language choice on the last page.
- [x] Propagate run mode (profile, debug) to attach command. https://github.com/flutter/flutter/issues/32999
Completed via engine changes; PR #4134 close w/o merging.
- [x] Add entry-point to run configurations. https://github.com/flutter/flutter/issues/31490
- [x] Add UI affordance to support continuously re-connecting the Android app during Flutter hot reload. https://github.com/flutter/flutter/issues/32824
- [x] Add UI affordance to trigger Flutter build aar. https://github.com/flutter/flutter/issues/26099
- [x] Add support for `flutter integrate` to existing Flutter module in AS. Currently it only hooks in include_flutter.groovy. https://github.com/flutter/flutter/issues/32993
- [ ] Launch devtools from Flutter attach button. (Are we sure we want to do this when we already have a button for it?) https://github.com/flutter/flutter/issues/33001
- [ ] Integration tests for IDE extensions. https://github.com/flutter/flutter/issues/33144

- **Phase 2**
- [ ] Investigate re-use of AS resource management to support use of Android resources by Flutter modules. https://github.com/flutter/flutter/issues/31501
- [ ] Doing the inverse (access Flutter resources in Android code) would require changes to the Android Studio code base.
- [ ] Add a custom Project Structure editor to manage all of pubspec.yaml. (Once again.)

- **Phase 3**
- [ ] Investigate possibility of adding support for Flutter modules to AS Project Structure editor (may require changing AS code base).

- **Phase 4**
- [ ] Investigate possibility of editing Flutter code as part of an Android project (requires changes to AS code base).
- [ ] Index C++ code and support library management -- might be free if previous item is implemented.

@devoncarew @xster