[BUGFIX] Do not escape nested tags in parseFunc

Due to the rector refactoring a line unset($currentTag) was removed,
resulting in text-elements with <p>something <a href="...">links</a>.</p>
did not detect a proper closing tag, resulting in broken HTML
in the output.

Additional tests properly check for this logic now.

Resolves: #90111
Related: #89807
Releases: master
Change-Id: I256dc42e3ff44548d43122d1984264ebaab40015
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/62889


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Susanne Moog <look@susi.dev>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Susanne Moog <look@susi.dev>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>