Split web audio feature

[jgraham]

The web audio feature appears to have it's baseline status set on the presence of api.AudioContext.AudioContext, but claims to cover a lot of other keys, not all of which are uniformly supported. In particular api.AudioContext.setSinkId isn't part of baseline, but also isn't covered by any other web feature. This seems misleading to developers, and is unhelpful to browser vendors trying to use web features to track functionality gaps.

[captainbrosset]

This sounds good to me.

@ddbeck provided this list of non-Baseline BCD keys in the feature: https://github.com/web-platform-dx/web-features/blob/2ff8aa41d6db82fd56dcf1159aa4d7d2703d1747/features/web-audio.yml.dist#L662C1-L751C72

We might want to look at these other non-Baseline keys to see if we should create other separate features.