Add PreferredVideoLabel Configuration to allow setting a preference when codecs are the same

[koenoe]

Have you read the FAQ and checked for duplicate open issues?
Yes

Is your feature request related to a problem? Please describe.
We currently have DASH manifests where we have both audio- and video tracks with the same codecs, but we'd still like to configure a preference. E.g. we have Dolby Atmos and Dolby Digital Plus audio tracks that use the ec-3 codec. In order to configure a preference we use preferredAudioLabel to choose one over the other (we've added labels to our manifest to facilitate this). We have a similar issue with video tracks, where we have HDR and SDR in hev1 codecs, but currently no way to configure a preference to choose one over the other. Especially during playback when ABR kicks in, it's not ideal for a user to constantly switch between HDR and SDR.

Describe the solution you'd like
I'd like a configuration like preferredAudioLabel where we can configure a preference apart from codec, I thought preferredVideoLabel would make sense.

Describe alternatives you've considered
We've played around with the setting preferredVideoHdrLevel but this only seems to help with PQ vs HLG, not for SDR.

Additional context
I'm not sure if this is the correct solution, but it makes sense to me. Happy to listen to alternative ideas or solutions. I'm eager to contribute as well, hence why I've already created a PR.

In order to start the discussion, or perhaps accept this change, I've submitted a PR (#5948) for this.