Initialize default components lazily in ExoPlayer.Builder to avoid
redundant component instantiations, useful in cases where apps
overwrite default components with ExoPlayer.Builder setters.
The fields in ExoPlayer.Builder are wrapped in a Supplier (rather than
just making then nullable and initializing them in
ExoPlayer.Builder.build()) so that we maintain the proguarding
properties of this class.
PiperOrigin-RevId: 406345976
