Further improves SectionComments

[live627]

• Use a more forgiving regex to detect slightly malformed section comments. Idea for further improvement: Use Utils::buildRegex() if available, because each comment is stripped to the bare words before building the final regex.
• Avoids removing and reinserting section comments that are already correct and in the proper location. This is explicitly checked for in the vendor-provided test suite.
• Defers removal of obsolete section comments until after analysis, reducing token stream mutations during processing. This improves fixer idempotency by avoiding unnecessary token modifications when no changes are required.
• Correctly preserves valid section comments while removing duplicates and misplaced comments.

My tests https://github.com/live627/php-cs-fixer-custom-fixers/blob/main/tests/SectionCommentsFixerTest.php

[live627]

Case                                       Tokens
-------------------------------------------------
all sections with phpdocs and enum            401
all sections and enum                         341
section comments missing a space              361
misplaced and duplicate section comments       93
completely wrong section comments              34