SDK / exoplayer

Util.getAudioTrackChannelConfig() maps a channel count to a
channel mask that is passed to AudioTrack. The method expected that
playback of 8-channel audio is possible from Android 5.1 and playback of
12-channel audio is only possible from Android 12L. However, there is no
restriction on the upper number of channels that can be passed to the
AudioTrack. google/ExoPlayer#10701 is an example where the audio decoder
outputs 12 channels on an Android 10.

This change removes the restrictions for 8 and 12 channels. Note, we still
do not support playback of arbitrary number of channels as it would require
further changes to DefaultAudioSink.

#minor-release

Issue: google/ExoPlayer#10701
PiperOrigin-RevId: 488659831
(cherry picked from commit 1b24e6fd)