Add system service for music recognition.

The client submits a RecognitionRequest via MusicRecognitionManager.  System server opens an audio stream based on the request and sends it to a MusicRecognitionService (which is exposed by a system app).  The result is passed back through system server to the original caller.

Test: tracked in b/169662646
Bug: 169403302
Change-Id: I4c7fd9d9d72ddd5678867fd037cab6198bff2c2d