Decouple the configuration from the AudioPolicyManager

Promote AudioPolicyConfig to a full class, not just a "view"
on the APM data. This allows separating initialization of
the APM config from the initialization of the APM itself.
Thus, the APM receives a fully initialized config upon
its creation, regardless of the way the config data has been
obtained.

Bug: 205884982
Test: atest audiopolicy_tests
Test: atest audiosystem_tests
Test: atest audio_health_tests
Test: m audiopolicy_fuzzer
Change-Id: I334d16e762499a0292540e6abae4e177480d6235