Update ExoPlayer usage

[jpelgrom]

Summary

Update the usage of ExoPlayer in the app:

• Migrate from the ExoPlayer v2 dependencies that are no longer supported to the new AndroidX Media3 - which marks several APIs as unstable, but according to Google can be ignored as we don't need binary compatibility
• Replace deprecated ExoPlayer functions with the non-deprecated alternatives
• Update the controls layout to be based on the new player view so it works correctly and it is not required to completely rewrite the controls - this copies the layout file from source as it is not possible to add/remove only a few buttons, tested and it works fine and API has been stable for ~3y now so I don't expect it will break

Also fixes a potential crash for dividing by 0 if the video ends before the frontend tells the app to stop.

Screenshots

The new player controls are a lot more modern and in my opinion nicer to use (alignment, animations, larger touch targets, dimmed video so you can see them):

Before	After

(before is incorrectly cropping the video, not sure why)

Link to pull request in Documentation repository

n/a

Any other notes