HTML API: Adjust code styling to Gutenberg's linter's preferences.

Adjust the code style according to the rules that the linting process in Gutenberg requires.

There are only a couple code changes that should have no effect on the runtime:
 - A missing check to verify that only `UTF-8` is supported has been added (brought up because it was identified as an undefined variable).
 - A few `return false;` statements have been added to avoid having the linter complain that functions don't return a value despite indicating they return `bool`. The functions are stubs for coming support and currently `throw`, so the `return` statements are unreachable.

Props dmsnell, costdev, davidbaumwald, peterwilsoncc, SergeyBiryukov.
Fixes #58918.
Built from https://develop.svn.wordpress.org/trunk@56363


git-svn-id: http://core.svn.wordpress.org/trunk@55875 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/html-api/class-wp-html-token.php

@@ -36,10 +36,12 @@ class WP_HTML_Token {
 	/**
 	 * Name of node; lowercase names such as "marker" are not HTML elements.
 	 *
-	 * For HTML elements/tags this value should come from {@see WP_HTML_Processor::get_tag}.
+	 * For HTML elements/tags this value should come from WP_HTML_Processor::get_tag().
 	 *
 	 * @since 6.4.0
 	 *
+	 * @see WP_HTML_Processor::get_tag()
+	 *
 	 * @var string
 	 */
 	public $node_name = null;