avcodec: update audio encoder to use ch_layout for channel ordering

It was introduced in 2022-03-15 - lavc 59.24.100 /lavu 57.24.100 , and channel_layout was deprecated and will be removed at some point.

One alternative with new API set would be just to set custom order, so we wouldn't need to reorder channels in vlc end, but I decided to go with smaller changes.

I tested this with 7.1 channel mp4 file for channel testing, checked with audacity on audio, encoded with ffmpeg and vlc and checked audio output with audacity to compare. Also tested that from 7.1 to stereo worked.