Reworking the media metrics getMetrics() calls (currently in MediaCodec,
MediaExtractor, MediaPlayer, and MediaRecorder) to fit new direction
from the API Council.
Drop the MediaMetricsSet that we had in the first round; go back
to a PersistableBundle as the return type. Moves the key definitions
from MediaMetricsSet.MediaCodec to MediaCodec.MetricsConstants
Bug: 37083862
Test: ran the corresponding CTS tests
Change-Id: I7905959ad2109887dd8fd16f0eb2831247abab2a
10353e3601