Improves the time taken to construct `playerInfo` from its bundle from ~450 ms to ~400 ms. Each `MediaItem` inside `Timeline.Window` contains `MediaMetadata` and hence is a good candidate for bundling optimisations. There already exists a test to check all parameters for null values when unset.
PiperOrigin-RevId: 495614719
(cherry picked from commit 8dea624c)
