[3.0] dav1d: always use buffers with the max resolution

When the super resolution of AV1 is used, some frames may be encoded smaller than the max resolution, but they are actually decoded at the max resolution by dav1d. So we need to provide a buffer large enough.

Ref. #28002 (closed)

For some unclear reason we don't need extra buffers in 3.0, unlike !3544 (merged). It might be related to the way the push model is decorelated from the vout.

The patch in 3.0 is different as the visible/decoded sizes are only set during NewPicture() where the only call to decoder_UpdateVideoFormat() is done.