Issue: google/ExoPlayer#9775
We got a few issues for this on GH already. Some RTSP servers do not provide
track timing in PLAY responses, or the timings are invalid.
Missing timing means the RTSP stream is not seekable. Added method to
1. Update the timeline that seek is not possible
2. Report read discontinuity so that playback can start from the beginning.
PiperOrigin-RevId: 423281439
