Both the extension OPUS decoder and the OMX/C2 MediaCodec
implementations for OPUS and VORBIS decode into the channel
layout defined by VORBIS. See
https://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-140001.2.3
While this is technically correct for a stand-alone OPUS or VORBIS
decoder, it doesn't match the channel layout expected by Android.
See https://developer.android.com/reference/android/media/AudioFormat#channelMask
The fix is to apply the channel mapping after decoding if needed.
Also add e2e tests with audio dumps for the extension renderer,
including a new 5.1 channel test file.
Issue: google/ExoPlayer#8396
#minor-release
PiperOrigin-RevId: 588004832
