[BUGFIX] Use class instead of HTML comment to determine loading state of IRRE element

IRRE relied on the HTML comment `<!--notloaded-->` to detect whether a
record is already loaded or not. As this might collide with HTML
minification, the comment has been replaced with a class placed in the
panel.

Resolves: #91258
Releases: master
Change-Id: Ibe890317bdcb9707a71de1168de0d404fb3c67a4
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/64385


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Xavier Perseguers <xavier@typo3.org>
Tested-by: Susanne Moog <look@susi.dev>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Xavier Perseguers <xavier@typo3.org>
Reviewed-by: Susanne Moog <look@susi.dev>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>