audio: Add example HAL implementation

This is partial implementation of the example V7.0 audio HAL
which passes VTS tests. Note that the 'core' part
of the HAL (IDevice/IStream) isn't implemented yet.
It passes VTS because it doesn't provide any devices
(modules) and the audio HAL isn't the 'default' instance.

Bug: 142480271
Test: atest VtsHalAudioV7_0TargetTest
      atest VtsHalAudioEffectV7_0TargetTest
Change-Id: Ie3dd62c5db1cdb5534df4dd7f326c4c8776bf3c4
Merged-In: Ie3dd62c5db1cdb5534df4dd7f326c4c8776bf3c4