[3.12] gh-137836: Support more RAWTEXT and PLAINTEXT elements in HTMLParser (GH-137837) (GH-140842) (GH-140850)

(cherry picked from commit a17c57eee5b5cc81390750d07e4800b19c0c3084)
(cherry picked from commit 0329bd11c7e98484727bbb9062d53a8fa53ac7fd)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>