[BUGFIX] Allow Fluid Preview for each Plugin

Allow individual Fluid templates for each Plugin
while Feature toggle "Fluid based page module" is
activated.

Resolves: #91920
Releases: master, 10.4
Change-Id: I52537dc2fcb61e16d78ed9bf71945a250a3f2f7f
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/65150


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Jörg Bösche <typo3@joergboesche.de>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Jörg Bösche <typo3@joergboesche.de>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>