audioservice: add RTT mode observer

Enable audio capture by the Assistant when RTT is ON during a call
similarly to when an accessibility service is in the foreground.

Also remove log when permission checked for hotword
and audio output capture fail as those checks are now done
systematically.

Also do not check permission to bypass interruption policy if
bypass flags are not set.

Bug: 132976361
Test: use voice input during a call with RTT enabled.
Change-Id: Iff45b0816dac889262ec29ea115f74dea4dc6b6d