[BUGFIX] Fix quoting and cleanup in AdminPanelView

In EXT:frontend/Classes/View/AdminPanelView.php add missing
htmlspecialchars() calls, remove unnecessary ones, add quoteJSvalues()
and do cleanup.

Resolves: #83357
Releases: master, 8.7
Change-Id: Ib546bcfaebf5342e187f8b707a9091947a97ca72
Reviewed-on: https://review.typo3.org/55116


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Mathias Schreiber <mathias.schreiber@typo3.com>
Tested-by: Mathias Schreiber <mathias.schreiber@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>