Revert "Revert "MediaCodec refactoring part 2-b: introduce BufferChannel""

- MediaCodec stops tracking the whole buffer array from OMX.
- BufferChannel handles array management instead, if necessary.
- MediaCodec delegates secure buffer management to BufferChannel.
- Remove sf2.

Bug: 32133435
Test: adb shell am instrument -e size small -w 'android.media.cts/android.support.test.runner.AndroidJUnitRunner'
Test: Play an encrypted content in Play Movies
Test: Mirror the screen via Cast.
Change-Id: I1ca705687956ad972e31257853c54e29cbd7181a