Add AAudioCommandQueue in aaudio service.

With AAudioCommandQueue, all the requests to aaudio service stream can
be turned into command and executed one by one. This can help reduce
multiple thread issue in aaudio service.

Test: atest AAudioTest
Test: run oboetester
Bug: 201000721
Change-Id: I81134e036d8921d327feb029d8fda725ce65d080