[BUGFIX] Fix fluid template paths to respect TypoScript order

Only add implicit default paths (Resources/Private/X) when they
are not explicitly configured via TypoScript, as they may have
been configured as an overwrite for another base path.

Resolves: #81099
Releases: main, 12.4, 11.5
Change-Id: I0fe4cb690aa253d5d9941fcfbe0a9c9063298547
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/80834


Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: core-ci <typo3@b13.com>