Fix sorting of uploads in encrypted rooms

[ofalvai]

Type of change

• Feature
• Bugfix
• Technical
• Other :

Content

Motivation and context

Fixes #2530

There are different loading mechanisms for encrypted and non-encrpyted rooms. The correct sorting was only applied to the non-encrypted codepath, this PR adds sorting to the encrypted codepath too.

Note: this PR won't fix the problem with lazy loading more pages of uploads in the encrypted codepath. I'm new to this codebase and don't see the full implications of that issue, but I'm happy to investigate that further in a separate PR.

Screenshots / GIFs

No screenshots for privacy reasons.

Tests

Open encrypted room with known media history.

Test 1: Open uploads list immediately, without scrolling back up in the timeline to load more media
Test 2: Scroll back in the timeline to cache media, then open uploads list

Tested devices

• Physical
• Emulator
• OS version(s): 11

Checklist

• Changes has been tested on an Android device or Android emulator with API 21
• UI change has been tested on both light and dark themes
• Accessibility has been taken into account. See https://github.com/vector-im/element-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-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
• If you have modified the screen flow, or added new screens to the application, you have updated the test UiAllScreensSanityTest.allScreensTest()

[bmarty]

Look good to me, thanks for your contribution!