Fix Cell broadcast sound in total silence

PlayerBase:
 Update player volume when the audio attributes are updated in case
we need to unmute
PlaybackActivityMonitor:
 Unmute alarm stream if needed when an alarm with flag
 FLAG_BYPASS_INTERRUPTION_POLICY starts from an app with
 privileged permission MODIFY_PHONE_STATE.

Bug: 63617557
Test: check sound with cell broadcast in total silence
Change-Id: Ifacb1d96a2d8d44047d9f9642d1e672fcf756cda