This is similar to the HLS fix in 770ca66fbc
Similar to HLS, the original problem here was **not** modifying the
`Format` for caption tracks
embedded into the video stream. I tried just updating the format in
both places, but that caused new failures because the new
('transcoded') format was then fed into `FragmentedMp4Extractor` as
part of `closedCaptionFormats`, which resulted in the CEA-608 data
being emitted from `FragmentedMp4Extractor` with the incorrect
`application/x-media3-cues` MIME type (but the bytes were actually
CEA-608), meaning the transcoding wrapper passed it through without
transcoding and decoding failed (because obviously CEA-608 bytes can't
be decoded by `CueDecoder` which is expecting a `Bundle` from
`CuesWithTiming.toBundle`.
To resolve this we keep track of the 'original' caption formats inside
`TrackGroupInfo`, so we can feed them into `FragmentedMp4Extractor`.
For all other usages in `DashMediaPeriod` we use the 'transcoded'
caption formats.
PiperOrigin-RevId: 592866262
f36ab87b38