Enable predictive back gesture

[frebib]

Content

Enable Android 15+ Predictive back gesture that was previously disabled
It only animates closing the app for now, but it's better than nothing.

Fixes #3795

Motivation and context

Google/Android want everything to support this eventually. It doesn't do anything special with Appyx animations yet, but at least it integrates with the OS and app-closing animations.
The mentioned bug, whilst still open, doesn't appear to happen any more, at least from my testing.

I have been running this patch for a couple of months and haven't really noticed any issues relating to it.
I will note that recently ~last month or so (?) I've been having issues with the keyboard not closing automatically when it should and I'm unsure whether it's caused by this patch, or some other upstream change/patch I'm carrying. Mentioning here mostly in case this gets merged and others report similar issues that coincide with the merge of this

Screenshots / GIFs

209d530b-cf50-41a3-9d01-5e34577784e2.mp4

Tests

• Use the app and notice that it doesn't seem to have any regressions, but the animations are nice.

Tested devices

• Physical
• Emulator
• OS version(s): Android 15, on Pixel

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 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
• Pull request includes a sign off
• You've made a self review of your PR

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

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Report is 15 commits behind head on develop.

Additional details and impacted files

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[jmartinesp]

I have been running this patch for a couple of months and haven't really noticed any issues relating to it.

I can't find any issues with it either, although the mentioned bug wasn't fixed by Google or at least it wasn't marked as fixed 🤔 .

@bmarty , @ganfra can I ping you for more thorough testing / opinions on this?

[bmarty]

If back press when a bottom sheet is displayed behave correctly, I guess we can take the risk to merge this PR.

[jmartinesp]

Approving this as I couldn't find any issues. Thanks!