SDK / exoplayer

This moves `SelectionOverride` from `DefaultTrackSelector`
to `TrackSelectionParameters`.

It is then use to allow track selection override per
track selection array.

Note that contrary to
`DefaultTrackSelector.Parameters.selectionOverride`, the renderer
concept is not exposed.

This cl is a part of the bigger track selection change,
splitted for ease of review.
Find all cls with the tag:
#player-track-selection

PiperOrigin-RevId: 399933612