Observe mic mute changes, consider recordingss paused when muted

Listen for the microphone mute state to change, and when it changes,
update the paused status of all audio recordings. If the mic is muted, then
every stream is considered paused.

Fixes: 168553482
Test: Get a call, then screen it. The "mic in use" icon should be
replaced by the mute icon

Change-Id: I5fad1f359c7009c924e8f7cce9c09f8ea299522a