[TASK] Centralize imagefile_ext, mediafile_ext and textfile_ext

Most access to the configuration options are made against AbstractFile
objects in FAL, which is now centralized in one place in AbstractFile.

This reduces errors when checking for file patterns.

Resolves: #90305
Releases: master
Change-Id: I7835d877bae1addf830ede3645ff8f1faa113052
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63155


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Susanne Moog <look@susi.dev>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Susanne Moog <look@susi.dev>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Benni Mack <benni@typo3.org>