SDK / exoplayer

Note:
- Fixing this uncovers another bug in how audio processor draining
  works, so the test playlist still doesn't play correctly after this
  change.
- Once we reconfigure the audio sink based on the ExoPlayer Format
  rather than the codec MediaFormat in a later change, this change can
  be reverted.

Issue: #6601
PiperOrigin-RevId: 281264149