Change animation on cold start by a fader animation.

[bmarty]

Also cleanup all our transition handler.

Content

Improve cold start by removing the sliding animation

Motivation and context

Improve UI

Screenshots / GIFs

Tests

• Kill the app
• Start the app
• Observe that the room list / login screen is displayed with a fader animation instead of a slider animation.

Tested devices

• [ ] Physical
• [x] Emulator
• OS version(s):

Checklist

• [ ] Changes have been tested on an Android device or Android emulator with API 24
• [ ] 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 title will be used in the release note, it clearly define what will change for the user
• [ ] Pull request includes screenshots or videos if containing UI changes
• [ ] You've made a self review of your PR

[github-actions[bot]]

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[bmarty]

Draft as it breaks animation where we may want to keep a slider like when the user signs out.

[sonarqubecloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov[bot]]

Codecov Report

:x: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 81.07%. Comparing base (73627d9) to head (c108ee4).

Files with missing lines	Patch %	Lines
...braries/architecture/animation/ScreenTransition.kt	0.00%	3 Missing :warning:
...ent/android/libraries/architecture/BaseFlowNode.kt	0.00%	1 Missing :warning:

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #5447      +/-   ##
===========================================
- Coverage    81.07%   81.07%   -0.01%     
===========================================
  Files         2317     2317              
  Lines        63628    63630       +2     
  Branches      8032     8032              
===========================================
  Hits         51588    51588              
- Misses        9104     9106       +2     
  Partials      2936     2936              

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[frebib]

I tried this out and immediately noticed that the room list doesn't slide left when opening and closing rooms. It's not bad; just a bit different. Is that an intentional side-effect?