
This allows MediaSources to accept MediaItem updates after creation. This CL adds the handling and plumbing logic in `ExoPlayerImpl`, `ExoPlayerImplInternal`, `MediaSourceList` and `MaskingMediaSource`. It also updates all forwarding/wrapping sources to forward these calls to their wrapped instance. The actual functionality is only added to `FakeMediaSource` instances in tests so far. PiperOrigin-RevId: 545450210