Migrate to non-transitive R classes

[Stypox]

What is it?

• Bugfix (user facing)
• Feature (user facing)
• Codebase improvement (dev facing)
• Meta improvement to the project (dev facing)

Description of the changes in your PR

• Replaces Migrate to non-transitive R classes #10077.
• Switch to non-transitive R classes, which became the default starting in Android Gradle plugin 8.0. This fixes build issues with the CI pipeline and helps speed up the build process.
• These were the cases where R.id.* did not exist anymore and had to be replaced by the fully-qualified path.
  • R.id.content -> android.R.id.content to find the root view of an activity. I tested this manually and it works.
  • R.attr.colorSecondary -> android.R.attr.windowBackground as the bottom toolbar background color. I don't know why it was colorSecondary before, but windowBackground yields the same color as before, I tested on API 33 and API 22 on all themes. Moreover windowBackground is defined directly in styles.xml, so it should be correct.
  • R.attr.colorAccent -> android.R.attr.colorAccent as the bottom toolbar foreground color. Again, I tested on API 33 and API 22 on all themes and noticed no difference.
  • R.attr.selectableItemBackground -> android.R.attr.selectableItemBackground
  • all exoplayer string/drawable resources (which btw are all private and are not meant to be used ;-) )

APK testing

The APK can be found by going to the "Checks" tab below the title. On the left pane, click on "CI", scroll down to "artifacts" and click "app" to download the zip file which contains the debug APK of this PR.

Due diligence

• I read the contribution guidelines.

[Isira-Seneviratne]

Looks good to me overall, there's one small change I'd recommend making.

[sonarqubecloud]

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 SonarCloud

[Stypox]

Merging, so that nightly testers can report bugs in case there is anything we missed. As explained in the PR description, I tested all changes and found no issue.