Remove MediaStreamConstraints dictionary from BCD

[queengooborg]

This PR removes the MediaStreamConstraints dictionary from BCD, folding its two parameters into the only function that uses it (api.MediaDevices.getUserMedia). This is also preliminary work for the removal of the MediaTrackConstraints dictionary as well.

[foolip]

Is there an MDN PR for this?

I don't think that capturing whether audio and video parameters are supported is the thing that matters to web developers, rather it's the next level, constraints like deviceId (all tracks), echoCancellation (audio tracks), or frameRate (video tracks). That's further complicated by exact and ideal in many contexts.

Ultimately I don't think https://github.com/mdn/browser-compat-data/blob/main/docs/data-guidelines.md#parameters-and-parameter-object-features will work here, because something like deviceId isn't one parameter, but a parameter that can appear in many places.

[saschanaz]

I'd like to use this data for automation, is there a written rule to name this? What happens when the spec changes the argument name, e.g. to constraintObject? Will the name here also change?

[foolip]

The rules are in https://github.com/mdn/browser-compat-data/blob/main/docs/data-guidelines.md#parameters-and-parameter-object-features. For the most part the names match the spec and I've been changing some to match, but I can't imagine they all match.

I would guess that in the vast majority of cases there's just one dictionary argument and the argument name can be ignored / assumed to match. That only leaves cases with multiple dictionary arguments needing to match on the name.

[queengooborg]

I've removed these subfeatures since their data matches their parent, and as indicated, there's no need for the individual audio and video features anyways!