audio policy: add forced uses for system

The volume and routing policy of AUDIO_STREAM_ENFORCED_AUDIBLE is
now controlled by AudioService by means of new forced use type
AUDIO_POLICY_FORCE_FOR_SYSTEM with config
AUDIO_POLICY_FORCE_SYSTEM_ENFORCED.

Property ro.camera.sound.forced is not used anymore.

Bug 7032634.

Change-Id: I742b0eebbe6b013f61d199846454a06411b52bc8
2 files changed