AV1 Transcoding Support, CRF=22

[subdavis]

Tested AV1 using this video from https://github.com/SPBTV/video_av1_samples/blob/master/spbtv_sample_bipbop_av1_960x540_25fps.mp4

Verified that browser will play av1 without transcoding, but that web and desktop are still choosing to transcode anyway because of VIAME support.

fixes #750
fixes #855

[BryonLewis]

Checked worker container ffmpeg, it's updated to the new version.
Tested AV1 encoded videos and they properly transcoded within the worker.
Desktop is a bit of a different story, but shouldn't prevent this PR from getting merged.
On desktop I believe we default to the VIAME version, then fall back to local ffmpeg so it won't have AV1 support unless VIAME updates or it isn't installed. I think we did this for windows support because it's less likely to have ffmpeg in the PATH. This may be related to my second question about informing the user when transcodes fail in a better way.

Two questions that don't need to be resolved in this PR:

• Should we enable mime-type for AV1 files. I don't think they are typically used, mostly they are mp4's by default anyways.
• ffmpeg version on desktop are variable between system and VIAME versions. They could have differing support for codecs. During testing I swapped back to the VIAME version ffmpeg and obviously it won't transcode AV1. We may want to make that error a little more known to the user because right now the job fails really fast with no notification unless the user goes to the job panel and the video acts like it should be displayed but doesn't.

[subdavis]

Should we enable mime-type for AV1 files. I don't think they are typically used, mostly they are mp4's by default anyways.

I was not able to determine a consistent mime for AV1. I think they'd mostly be mp4 or avi.

ffmpeg version on desktop...

Might be nice to let the user choose between system ffmpeg and viame ffmpeg in a dropdown on the settings page. Improving job error and success reporting I agree would be nice, and should be its own thing.