HTML API: Reconsume script data less-than tokens

[sirreal]

What changed

Updates WP_HTML_Tag_Processor::skip_script_data() so a non-matching byte after < in script data is reconsumed instead of skipped.

Adds regression coverage for normalize() and tag parsing cases such as <script><</script> and <script></</script>, plus related less-than sequences before the real closer.

Why

The parser was advancing past the byte after < when the sequence was not a script end tag. If that byte was itself another < starting the real </script> closer, the parser skipped over the closer and later reported the document as paused at an incomplete token. normalize() then dropped the script element.

Validation

• WP_TESTS_SKIP_INSTALL=1 ./vendor/bin/phpunit --group html-api --filter 'test_special_text_less_than_sequences_before_closer_are_not_incomplete|test_script_tag_parsing' -> OK, 45 tests, 83 assertions
• ./vendor/bin/phpcs --standard=phpcs.xml.dist src/wp-includes/html-api/class-wp-html-tag-processor.php tests/phpunit/tests/html-api/wpHtmlProcessor-serialize.php tests/phpunit/tests/html-api/wpHtmlTagProcessor.php -> OK
• Worker run also reported WP_TESTS_SKIP_INSTALL=1 ./vendor/bin/phpunit --group html-api,html-api-html5lib-tests -> OK, 2917 tests, 6182 assertions, 421 skipped

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