HTML API: Add tests confirming comment behavior in HTML Processor.
There was a bug-fix late in the 6.6 cycle in the HTML Processor which
resolved an issue with the wrong name being reported when paused at
processing-instruction look-alike invalid comments, but no tests were
added to enforce the correct behaviors.
This patch adds the missing tests.
Developed in https://github.com/WordPress/wordpress-develop/pull/6765
Discussed in https://core.trac.wordpress.org/ticket/61530
Follow-up to [58304], [58558].
Props dmsnell, jonsurrell.
See #61530.