[Rich text editor] Add feature flag for rich text editor

[jonnyandrew]

Type of change

• Feature
• Bugfix
• Technical
• Other :

Content

Add feature flag for the rich text editor.

When the feature flag is disabled, markdown support is enabled.

Motivation and context

• [Story] RTE Plain/Markdown text mode on EX element-meta#1936
• Fixes Punctuation marks are prefixed with backslashes in message body #1260

Screenshots / GIFs

Screen_recording_20230912_174836.webm

Tests

• Install a debug version of the app
• Toggle the new setting in developer settings
• Create a message with markdown
• Edit a message with markdown
• Reply to a message with markdown

Tested devices

• Physical
• Emulator
• OS version(s): 13

Checklist

• Changes have been tested on an Android device or Android emulator with API 23
• UI change has been tested on both light and dark themes
• Accessibility has been taken into account. See https://github.com/vector-im/element-x-android/blob/develop/CONTRIBUTING.md#accessibility
• Pull request is based on the develop branch
• Pull request includes a new file under ./changelog.d. See https://github.com/vector-im/element-x-android/blob/develop/CONTRIBUTING.md#changelog
• Pull request includes screenshots or videos if containing UI changes
• Pull request includes a sign off
• You've made a self review of your PR

[jonnyandrew]

The naming reflects that the rich text editor is not actually toggled; it is still always running under the hood. Only the text formatting capabilities of the RTE may be disabled (i.e. HTML output ignored and formatting buttons hidden)

[ElementBot]

	Warnings
⚠️	features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/messagecomposer/AttachmentsBottomSheet.kt#L24 - Using a material import while also using the material3 library
⚠️	gradle/libs.versions.toml#L13 - A newer version of androidx.core:core-ktx than 1.10.1 is available: 1.12.0
⚠️	gradle/libs.versions.toml#L96 - A newer version of androidx.compose.material3:material3 than 1.2.0-alpha06 is available: 1.2.0-alpha07

Generated by 🚫 dangerJS against b584996

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[codecov]

Codecov Report

Patch coverage: 52.50% and no project coverage change.

Comparison is base (8abaee8) 57.69% compared to head (b584996) 57.69%.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1289   +/-   ##
========================================
  Coverage    57.69%   57.69%           
========================================
  Files         1087     1087           
  Lines        28618    28643   +25     
  Branches      5861     5865    +4     
========================================
+ Hits         16510    16526   +16     
- Misses        9535     9542    +7     
- Partials      2573     2575    +2     

Files Changed	Coverage Δ
...ries/featureflag/impl/StaticFeatureFlagProvider.kt	0.00% <0.00%> (ø)
...nt/android/libraries/matrix/api/room/MatrixRoom.kt	33.33% <ø> (ø)
...droid/libraries/matrix/impl/room/RustMatrixRoom.kt	0.00% <0.00%> (ø)
...ent/android/libraries/textcomposer/TextComposer.kt	54.94% <0.00%> (-0.16%)	⬇️
...ges/impl/messagecomposer/AttachmentsBottomSheet.kt	40.00% <25.00%> (-1.51%)	⬇️
...ndroid/features/messages/impl/MessagesPresenter.kt	81.92% <66.66%> (-0.33%)	⬇️
...nt/android/features/messages/impl/MessagesState.kt	100.00% <100.00%> (ø)
...id/features/messages/impl/MessagesStateProvider.kt	90.24% <100.00%> (+0.24%)	⬆️
...ent/android/features/messages/impl/MessagesView.kt	58.41% <100.00%> (+0.20%)	⬆️
...ssages/impl/messagecomposer/MessageComposerView.kt	54.05% <100.00%> (+4.05%)	⬆️
... and 3 more

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[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
No Duplication information

[bmarty]

LGTM, thanks!