HLS distinguishes between 'subtitles' (WebVTT or TTML distributed in
separate files with their own playlist) and 'captions' (CEA-608 or 708,
distributed muxed into the video file).
The format transformation added in 7b762642db
only applies to subtitles and not captions. This change makes the same
transformation for caption formats.
This resolves an error like:
```
SampleQueueMappingException: Unable to bind a sample queue to TrackGroup with MIME type application/cea-608.
```
Also add two playback tests for HLS CEA-608, one that parses during
decoding (old way) and one during extraction (new way). Adding these
tests is what alerted me to this issue.
PiperOrigin-RevId: 592571284
770ca66fbc