avcodec: pass coded dimensions to hardware decoder

Regression from b71c85b3d88b8d0ad2d4a63bf58ebcd2ad771cbf.
avcodec: allow frame threading with hardware acceleration

Only MPEG1/2 slice threading is currently known as broken.

This rectifies commit df252eac618091d156cf986f38a98c2bddbc8437.
vda: drop priority to zero (refs #8927)
vaapi: drop priority to zero

The plugin does not correctly check decoder profiles, so it should
really not be enabled automatically. It can still be enabled manually
from the UI or CLI as before.
dxva2: drop priority to zero for the time being
avcodec: autodetect hardware acceleration by default
Remove older iOS vout
AndroidSurface: fix compilation regression from ffcfa6daa7
po: add hwdummy
avcodec: fix potential multiple free of hwaccel module
avcodec: list all pixel formats, then try hardware acceleration
avcodec: simplify thread support checks
Fix sizeof mismatch (cid #1049623 and #1049622)
Fix sizeof mismatch (cid #1049621)
Fix sizeof mismatch (cid #1049620)
FIx sizeof mismatch (cid #1049619)
Fix sizeof mismatch (cid #1049614 and #1049613-12)
FIx sizeof mismatch (cid #1049611)
Fix memory leak (cid #1049576)
Fix memory leak (cid #1049575)