Better control of when MediaCodec has data for mediametrics

Identify some marker points (configure, release, destruction) where we
can state we have metrics data to dump. Otherwise, we were dumping
skeletal records into the metrics stream causing extra traffic of no
value.

Bug: 274253278
Test: examination of emitted mediametrics data
Change-Id: I60e2ffa19b9d6597447c916a63b02b1f5c1fa37d