Add SVT-AV1 codec

[at-wat]

Implement AV1 codec using SVT-AV1.
Encoding 640x480 video with preset=8 seems reasonable on today's CPUs.

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Reference SVT-AV1 library usage: https://github.com/FFmpeg/FFmpeg/blob/master/libavcodec/libsvtav1.c

[codecov]

Codecov Report

❌ Patch coverage is 74.10072% with 36 lines in your changes missing coverage. Please review.
✅ Project coverage is 42.95%. Comparing base (5aad703) to head (4cd2e7d).

Files with missing lines	Patch %	Lines
pkg/codec/svtav1/svtav1.go	72.80%	25 Missing and 9 partials ⚠️
pkg/codec/svtav1/params.go	85.71%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #660      +/-   ##
==========================================
+ Coverage   42.19%   42.95%   +0.76%     
==========================================
  Files          82       84       +2     
  Lines        5660     5799     +139     
==========================================
+ Hits         2388     2491     +103     
- Misses       3126     3153      +27     
- Partials      146      155       +9     

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