[Feature] Android App Screen Sharing True Fullscreen

[JonathanMBrand]

Issue:
When someone is sharing their screen on a call, there is a full-screen button to enlarge the shared video. However, on the Android app, this does not make the stream fill the entire phone's screen, which is very confusing and annoying.

Possible fixes:

• Change fullscreen button behaviour to make the video fit the actual full screen of a phone on the app
• Change the icon for the current full-screen button to e.g. theatre mode and add a new actual full-screen button to enlarge videos to fill the entire phone screen

Further comments:

• This might be a matrix limitation, but it would be good if there was also an option to be in a voice chat without automatically seeing the screen sharing stream, similar to how screensharing functions in discord