Reimplement audio selector logic

[lherman-cs]

[lherman-cs]

Todo: bizarre bug on the third participant.

Steps to reproduce (use meet.pulsebeam.dev):

1. Connect P1
2. Connect P2
3. Connect P3
4. Mute P1 and P2.
5. Starts talking from P3. The audio will have high latency, and sometimes can't be heard.

So far, this is reproducible only locally.