New Anki Editor migration

Upstream moved the note editor's control from Python to TypeScript and now serves it as a backend web page ([ankitects/anki#4029](https://github.com/ankitects/anki/issues/4029), tracking [ankitects/anki#3830](https://github.com/ankitects/anki/issues/3830)) the same mechanism we already use for deck options, graphs, card-info, etc. This proposes bringing that editor into AnkiDroid behind a developer-options flag, reusing the existing AnkiServer stack.

- The legacy NoteEditorFragment stays the default. Relates to [#10751](https://github.com/ankidroid/Anki-Android/issues/10751) and [#1377](https://github.com/ankidroid/Anki-Android/issues/1377).

## High-level steps (in order)
- Backend bump: In Anki-Android-Backend, move the anki submodule past [#4029](https://github.com/ankitects/anki/issues/4029)
- Consume the new backend in AnkiDroid
- Add the experimental flag and create the editor fragment
- Port the host bridge to Kotlin
- Close the mobile gaps (also see what we need to do differently in AnkiDroid than upstream)
- Testing (Unit test and user testing i.e. since it will be experimental)