av1: Fix handling of alignment in caps
Originally, everything was secretly TU, and life was good. But now we have introduce various alignments without updating the muxers and demuxers. So that kind of work, cause in most case av1parse will default to TU. But when it does not, it breaks in various ways. I've first detected this with a stateless decoder that requires frames, alignment that wasn't always right.
- Fix ISOMP4 to advertise TU
- Fix matroskamux to do the same
- Fix the parser, so it won't assume nothing has to be done, when upstream did not set the alignment field.
Fixes #1010 (closed)