libaaudio: API changes requested by council

Change AAudioStream to not be a pointer. Now it is just a struct.
Change AAudioStreamBuilder to not be a pointer. Now it is just a struct.
Change aaudio_audio_thread_proc_t to be a pointer to a proc.
Fix prototype of AAudioStream_getDeviceId().

Bug: 30210002
Test: CTS test_aaudio.cpp
Change-Id: Ia5a277a53ac64e93d75de4f196aa167998522c03
Signed-off-by: Phil Burk <philburk@google.com>