aaudio: add MediaMetrics for MMAP streams

Log events from service.
Log start, stop, disconnect and other events.
Log underruns and bufferSize.

Bug: 154543374
Test: adb shell dumpsys media.metrics --clear
Test: run an app that uses MMAP, like OboeTester
Test: adb shell dumpsys media.metrics
Test: Expect to see lots of "audio.stream" events.
Change-Id: I690e5226b695d53d038d644f4438c759e08f9fbb