This is a step towards adding general support for overlapping
subtitles in these formats (and others), both muxed and sideloaded:
* Issue: google/ExoPlayer#10295
* Issue: google/ExoPlayer#4794
This change adds these files to the end-to-end playback tests too, but
the subtitle track is currently disabled because renderer-side subtitle
parsing causes flaky tests (due to an uncontrolled thread in
`SimpleSubtitleDecoder`). The subtitle track will be re-enabled in
a follow-up change when loading-side subtitle parsing is added (so the
tests will no longer be flaky). At this point the overlapping subtitles
**still** won't be supported end-to-end, but a second change will
resolve this will changes in `TextRenderer` - which will change the
end-to-end playback dumps to reflect the overlapping subtitles.
PiperOrigin-RevId: 548705032
34768c2399