Level codec fixes for Dolby Vision and filtering of unknown codecs

[robwalch]

This PR will...

Add Dolby Vision four CCs and filter out levels with unknown codecs mixed with levels with known codecs.

Why is this Pull Request needed?

This allows HLS.js to properly filter out levels with Dolby Vision codec strings in browser without support. Where these codecs are supported, SourceBuffers will be created with the correct mime-type strings (#4744).

In the case where HLS.js encounters unknown codecs (as was the case with dvh1 and dva1), since unknown codecs are not filtered using isTypeSupported, they will be removed as long as there are levels that remain that passed the support check.

Resolves issues:

Related to #4744 (This change may resolve that issue if it is an artifact of the SourceBuffer being created with the wrong codec string).

Other considerations:

This is a small change to improve variant filtering and SourceBuffer creation. It does not include robust HDR support with HDR/SDR selection or MediaCapabilities filtering. That will be covered by #2489 and other issues slated for v1.5.

Checklist

• changes have been done against master branch, and PR does not conflict
• new unit / functional tests have been added (whenever applicable)
• API or design changes are documented in API.md

[cjpillsbury]

Makes sense. 👌 We may want a followup to avoid mismatches between supported codecs in a given env and our hardcoded list, but that feels out of scope here.