HTML API: Use full parser in html5lib tests.

Previously the `html5lib` tests have only run in the fragment parser mode,
assuming IN BODY context. This limited the number of tests which could run
and was a result of the HTML Processor only supporting the IN BODY fragment
parser. In [58836], however, a full parser was added to the HTML Processor.

In this patch the full parser is utilized in order to run more of the
previously-skipped tests, asserting more behaviors in the HTML parsing.

Developed in WordPress/wordpress-develop#7117
Discussed in https://core.trac.wordpress.org/ticket/61646

Props: dmsnell, jonsurrell.
See #61646.

Built from https://develop.svn.wordpress.org/trunk@58859


git-svn-id: https://core.svn.wordpress.org/trunk@58255 1a063a9b-81f0-0310-95a4-ce76da25c4cd

Author: dmsnell

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.7-alpha-58858';
+$wp_version = '6.7-alpha-58859';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.