add getMetrics() apis for AudioTrack and AudioRecord

add getMetrics() method to access media.metrics for AudioTrack and
AudioRecord. Includes the code paths and the sdk documentation
for the keys and what they return.

Moves the media metrics JNI support routines from media to core
to support these audiotrack/record operations being there; still
accessible to the existing operations in the media libraries.

Bug: 72179020
Bug: 72178968
Test: enhanced CTS
Change-Id: I3f05beba31aacb9b96854f8a774cb8f669ee1625