Update Default AudioControl AIDL HAL for version 2

- Add Gain Callback to notify unexpected gain changed from HAL
(as currently done for Audio Focus).

- Add dumpsys commands

Bug: 154906631
Test: build and run VTS tests

Signed-off-by: Francois Gaffie <francois.gaffie@renault.com>
Change-Id: I6be9620feb19d766d43be7199be2e9cd6d63c644