SDK / exoplayer

This change moves the default logic into the actual Player
implementations, but does not introduce any behavior changes compared
to addMediaItems+removeMediaItems except to make the updates "atomic"
in ExoPlayerImpl, SimpleBasePlayer and MediaController. It also
provides backwards compatbility for cases where Players don't support
the operation.

Issue: google/ExoPlayer#8046

#minor-release

PiperOrigin-RevId: 534945089
(cherry picked from commit 6309b11792b05306d004747af35d67f32a352782)