HTML API: Refactor wp_strip_all_tags()

[dmsnell]

Trac ticket: Core-65984.

Rewrites the logic of wp_strip_all_tags() to rely on the HTML API rather than on strip_tags(), due to the challenges strip_tags() has with properly parsing HTML. The new version of the function returns renderable text nodes, normalized and re-escaped for more predictable inputs into downstream parsers.

Notable changes

• The contents of SCRIPT and STYLE tags used to be lifted out of the elements, which led to data corruption, as these contents are not intended to be renderable with the rest of the text nodes. These are no longer included in the function outputs; the same is true for the “special atomic elements” defined by the HTML API (IFRAME, TEXTAREA, TITLE, etc…)
• Text contents are decoded and then re-encoded to normalize the use of character references.
• wp_html_excerpt() previously truncated early when the number of characters requested fell inside an HTML character reference, but since character references are now decoded before truncating, the function should more reliably return a string of the requested count of code points.
• When generating the CSS for font faces, instead of running the entire generated CSS snippet through wp_strip_all_tags(), each declaration runs its property and values separately through wp_strip_all_tags(). This removes some corruption that occurred when there were spans of text resembling incomplete HTML syntax tokens.

[github-actions]

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[github-actions]

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