Charset: wp_has_noncharacters() for more-specific Unicode handling.
Noncharacters are code points that are permanently reserved in the Unicode Standard for internal use. They are not recommended for use in open interchange of Unicode text data. However, they are valid code points and will not cause a string to return as invalid.
Still, HTML and XML both impose semantic rules on their use and it may be important for code to know whether they are present in a string. This patch introduces a new function, wp_has_noncharacters(), which answers this question.
See https://www.unicode.org/versions/Unicode17.0.0/core-spec/chapter-23/#G12612
Developed in https://github.com/WordPress/wordpress-develop/pull/9827
Discussed in https://core.trac.wordpress.org/ticket/63863
See #63863.