picture_Setup: missing const
rawvideo: use chroma desc, follow dimensions set by the demuxer

Refs #10722, refs #10723. Also fix a small leak on error.
caopengllayer: improved main thread synchronization and locking

Grouping of 2 sync calls into one, use of CATransaction lock / unlock instead of being / commit and introduction of GCD

Signed-off-by: Felix Paul Kühne <fkuehne@videolan.org>