Android: Detect internal mic/audio out and enable Mute Myself by default

[ann0see]

Another idea before I forget to write it down...

It would be nice to have if the Android audio system could check whether it's only got the internal mic / audio out connected. If so, it should turn on "Mute Myself" and prevent it being turned off. (Maybe have a different banner - so we'd have "unmuted", "self-muted" and "hard muted".)

Originally posted by @pljones in #2457 (comment)

[ann0see]

I wouldn't hard mute anywhere, but handle it similar to SonoBus:
Give a warning and state that feedback might occur but allow the user to unmute themselves (we shouldn't disallow the user to unmute themselves)

MAINTENANCE: Please change this issue issue description to fit the best needs.

[dcorson-ticino-com]

Why limit this to just Android ?

[pljones]

Because it would be at platform level, not common across platforms. However, it would need cross-platform support to make it work for even just one. That means future changes could be made to support other platforms.

If you've a contribution for one of the other platforms that enables this in a cross-platform manner, please put the code up for review and reference this issue.