[BUGFIX] Properly compare file extensions in ResourceFileExtensionMatcher

It's now ensured that ResourceFileExtensionMatcher
properly compares  the file extensions using only
lowercase chars. Additionally, the in_array checks
are set to "strict".

Resolves: #100250
Releases: main
Change-Id: I687d69d1b2b550f45245ddeac5b09bf3581eff2f
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78726


Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: core-ci <typo3@b13.com>