Exposes {start,stop}AudioSource to JAVA layer

- Android Automotive directly calls AudioSystem at the time being,
AudioManager is not updated in this CL

TODO:

- AudioPolicyManager::connectAudioSource is a no-op for
AUDIO_DEVICE_API_VERSION_3_0

Bug: 112161027
Test: m -j
Change-Id: I27a28cd1fd2992c4a7a9a67feb606f35cae43cc3