gh-102555: Fix comment parsing in HTMLParser according to the HTML5 standard (GH-135664)

* "--!>" now ends the comment.
* "-- >" no longer ends the comment.
* Support abnormally ended empty comments "<-->" and "<--->".

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Co-author: Kerim Kabirov <the.privat33r+gh@pm.me>
Co-authored-by: Ezio Melotti <ezio.melotti@gmail.com>