Relax Global Styles custom CSS filters to allow arbitrary CSS.
Escape HTML characters `<>&` in Global Styles data to prevent it from being mangled by post content filters. The data is JSON encoded and stored in `post_content`. Filters operating on `post_content` expect it to contain HTML. Some KSES filters would otherwise remove essential CSS features like the `<custom-ident>` CSS data type because they appear to be HTML tags.
[61418] changed STYLE tag generation to use the HTML API for improved safety.
Developed in https://github.com/WordPress/wordpress-develop/pull/10641.
Props jonsurrell, dmsnell, westonruter, ramonopoly, oandregal, jorgefilipecosta, sabernhardt, soyebsalar01.
See #64418.
Built from https://develop.svn.wordpress.org/trunk@61486
git-svn-id: http://core.svn.wordpress.org/trunk@60798 1a063a9b-81f0-0310-95a4-ce76da25c4cd
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