Currently only 2 options are implemented, mainly aimed at helping troubleshoot
audio related problems:

- Disable native call integration (it disables CallKit / ConnectionService)
- Disable P2P

🔥🔥🔥

Move it away from AbstractApp into an auxiliary function. In addition, introduce
a new `getServerURL` function which gets the configured server URL and defaults
to meet.jit.si as before.

We started on the way to responsive UI and its design with aspect ratio
and keeping the filmstrip on the short side of the app's visible
rectangle.

Shortly, we're going to introduce reduced UI for Picture-in-Picture. And
that's where we'll need another dimensions-based detector akin to the
aspect ratio detector.

While the AspectRatioDetector, the up-and-coming ReducedUIDetector, and
their base DimensionsDetector are definitely separate abstractions and
implementations not mixed for the purposes of easy extensibility and
maintenance, the three of them are our building blocks on top of which
we'll build our responsive UI.

[RN] Fix PR feedbacks, write persistency docs