Restore MarkdownTextInput contents

[jmartinesp]

Type of change

• Feature
• Bugfix
• Technical
• Other :

Content

• Add a MarkdownTextInputStateSaver to keep its contents when going to a sub-screen and coming back to it (these are not drafts).
• Also add default text flags for the MD composer.

Motivation and context

Fixes #2898.
Fixes #2896.

Screenshots / GIFs

md_restoration.mp4

Tests

• Go to any room.
• Type something in the message composer.
• Open another screen (room info, other user's details, call, etc.).
• The unfinished message should be there when you come back to the room screen.

Tested devices

• Physical
• Emulator
• OS version(s): 14

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/element-hq/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/element-hq/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

[github-actions]

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarCloud

[codecov]

Codecov Report

Attention: Patch coverage is 10.00000% with 18 lines in your changes are missing coverage. Please review.

Project coverage is 74.18%. Comparing base (06d5376) to head (813219d).

Files	Patch %	Lines
...ries/textcomposer/model/MarkdownTextEditorState.kt	0.00%	17 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2902      +/-   ##
===========================================
- Coverage    74.21%   74.18%   -0.04%     
===========================================
  Files         1540     1540              
  Lines        36892    36911      +19     
  Branches      7149     7152       +3     
===========================================
+ Hits         27381    27382       +1     
- Misses        5779     5796      +17     
- Partials      3732     3733       +1     

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[bmarty]

LGTM, thanks!