Improve CurrentMediaItemTracker

[StaehliJ]

As a user / integrator I want to be able to use custom MediaItemTracker by specify an url and a media id

Issue

Currently MediaItemTracker are not setup correctly when the input MediaItem has an url and a media id set and the MediaItemTrackerData is set after in a MediaItemSource.

Acceptance criteria

• CurrentMediaItemTracker start / update / stop tracker when needed.
• MediaItemTracker.update is called only when data has changed.
• Tracker are stop and restart if allowed when PillarboxPlayer.replaceMediaItem is called with not the same data.

Tasks

• Add unit tests to covers all cases.
• Improve current MediaItem changes detection.