SDK / exoplayer

We currently only end sessions on Timeline updates if the associated media
is no longer in the playlist. But we should also end all sessions that are
finished as a result of the timeline update (similar to how this is done for
discontinuities). This issue was introduced by https://github.com/google/ExoPlayer/commit/394ab7bcfd53bc8ffb8d2e37a5aeb71fef04d13c

PiperOrigin-RevId: 423075855