MediaMetrics: Prepare statistics for protos

1) Add AudioRecord to Analytics trigger.
2) Log RecordThread statistics.
3) Rename DURATIONNS to EXECUTETIMENS to avoid confusion.
4) Use streamType from server not client.
5) Split MMAP types to MMAP_PLAYBACK and MMAP_CAPTURE.
6) Use string flags for AudioTrack and AudioRecord.
7) Compute underrun frames for MixerThread.
8) Log BT connection state.

Test: adb shell dumpsys media.metrics
Test: atest mediametrics_tests
Test: adb shell dumpsys stats --metadata
Bug: 149850236
Change-Id: Iacf3f117c00ec9f377e62862080252aef9dc084f