Support for simultaneous USB Audio Devices connect/disconnect

Attach/Detach logic
Decoupling card# and list index
Modern loop constructs
Consistent logging flags
Add class/type flags to device "address" string.
Factored UsbAudioDevice out of UsbAudioManager.

Bug: 18399845
Bug: 18717784

Change-Id: I6f185e1c24091d4c0d21eb7e922a1496748d32c3