feat(FormatUtils): Support multiple audio tracks in the DASH manifest

[absidue]

Description

Currently the DASH manifest doesn't include any language or default track information, which is fine for videos that only have a single audio track/language, as the player will just pick the first audio format that it can play, however for videos with multiple different audio track in different languages, that means that the player still picks the first one it can play, which is likely to be in a different language than the original video audio. For Mr. Beast videos that means listening to the video in Arabic, with no way to change it.

If the video has multiple languages, this pull request adds the language and default track information to the DASH manifest. I also added the audioSamplingRate, as the DASH specification says that it should be included in the manifest, that will now be included for all audio formats regardless of whether the video has multiple languages or not.

So far I've only tested these changes with FreeTube and video.js correctly selected the default track and also picked up on the different languages (as we don't have a language picker yet you have to dig around in video.js at runtime to notice that it knows about the different languages). So testing this with other players might be a good idea.

https://dashif-documents.azurewebsites.net/DASH-IF-IOP/master/DASH-IF-IOP.html#audio-constraints

Type of change

• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have checked my code and corrected any misspellings