KSES: Replace attribute parsing with HTML API.

[dmsnell]

In this patch several kses functions have been rewritten to rely on the spec-compliant parsing made available in the HTML API. These functions convert HTML input into an array of parsed attribute values. By relying on the HTML API it's possible to recognize the HTML in the same way that a browser would, removing a layer of custom interpretation, full of discrepancies and bugs.

[github-actions]

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