Add AV1 as a preferred codec option

[Insprill]

This adds AV1 as an option for the preferred codec in addition to H264/5, and allows it to be used as a last-resort if other formats are unavailable. This could be considered a follow-up to #545, since it only allowed AV1 to be direct-played, not transcoded.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 21.90%. Comparing base (9eb9cd1) to head (9fa102e).
Report is 12 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #892      +/-   ##
==========================================
+ Coverage   21.86%   21.90%   +0.03%     
==========================================
  Files          63       63              
  Lines        8630     8634       +4     
  Branches     1585     1587       +2     
==========================================
+ Hits         1887     1891       +4     
+ Misses       6724     6722       -2     
- Partials       19       21       +2     

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[oddstr13]

Don't mind the code coverage report, adding tests for most things in this project is difficult.

[oddstr13]

Needs a rebase due to the HEVC PR touching the same file region.
That same PR added tests covering this function, so those tests need updating to account for the changes here.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[oddstr13]

Looks good, I just need to find a way to test if it actually works

[oddstr13]

It works? Probably, sort of?
My server was screaming bloody murder, and my Kodi client didn't wanna play the video, only audio (I'm stuck on Kodi 20).

So, this PR works, after enabling AV1 transcoding on the server, but it doesn't actually work for me.

I tested by setting AV1 as the preferred codec, and enabling transcode HEVC.