Deprecated field `MediaItem.playbackProperties` remains for backwards compatibility, but its type is changed from `MediaItem.PlaybackProperties` to `MediaItem.LocalConfiguration`. The private `MediaItem` constructor will now also take in a `LocalConfiguration` argument instead. PiperOrigin-RevId: 535648420 (cherry picked from commit b89cc652e5d466591617bfb5c9183a033cdf74b9)