Currently, TrackSelectionOverrides are documented as being applied
per track type, meaning that one override for a type disables all
other selections for the same track type. However, the actual
implementation only applies it per track group, relying on the
track selector to never select another renderer of the same type.
This change fixes DefaultTrackSelector to fully adhere to the
TrackSelectionsOverride definition. This solves problems when
overriding tracks for extension renderers (see Issue: google/ExoPlayer#9675)
and also simplifies a workaround added to StyledPlayerView.
#minor-release
PiperOrigin-RevId: 409121711
Where this introduced an inconsistency (e.g. assigning to something
called `windowIndex`), I generally renamed the transitive closure of
identifiers to maintain consistency (meaning this change is quite
large). The exception is code that interacts with Timeline and Window
directly, where sometimes I kept the 'window' nomenclature.
#minor-release
PiperOrigin-RevId: 407040052
