Adding support for dynamic audio gain config

Automotive OEMs need a mechanism to update vehicle-based
audio port configurations during run-time. This can be
achieved mostly through core audio hal aidl interface,
namely IModule::getAudioPorts(). However it also limits the
ability of audio hal since it is expected to maintan unchanged
configuration for given audio device ports and have it
available before audio framework initializes, which is
not always the case.

The following usecases are under consideration for this
feature:
1. Audio gain stages updated at end-of-line/factories as
   runtime configurations.
2. Audio gain stages  are stored outside of android partition
   (example - an external amplifier) and needs dynamic query
   post boot up. Availability at service init is not  guaranteed
   since ECU lifecycles are not necessarily synchronized.
3. Audio gain stage updates based on user subscriptions
   to enable advanced signal processing capabilities.

This change:
- Adds a new set-api for callback to report changes to
  audio hardware module. It is expected that in future the
  same interface can serve as callback to multiple categories
  of configs (other than audio gain stages).
- Adds a new clear to remove callbacks.
- Adds a new callback interface for changes to audio port
  configs. For the time being, car framework shall only support
  changes to audio gain stages.

Bug: 261647905
Test: VTS test

Change-Id: I5891e324f2d909a9c5fe30c47ad30e23e74ec6c4
Signed-off-by: Raj Goparaju <rajgoparaju@google.com>