Make own preview window smaller or option to disable

[stefonarch]

At the moment making a video call the own webcam view is quite big related to the counterpart.
Describe the solution you'd like
Adding an option to customize it's size or make it smaller would be a solution, maybe somebody would like also an option for disabling it (or fading out after some sec).

[SimonBrandner]

Closing in favour of #18262