SDK / exoplayer

- DefaultAudioSink always supports floating point input. Make it
  advertise this fact.
- Remove the ability to enable/disable floating point output in
  FfmpegAudioRenderer, since this ability is now also provided on
  DefaultAudioSink.
- Let FfmpegAudioRenderer query the sink to determine whether it
  will output floating point PCM directly or resample it to 16-bit
  PCM.

PiperOrigin-RevId: 320945360