[!!!][TASK] Cleanup and remove old filefunc logic

The BasicFileUtility was used before FAL also for
checking file mounts and paths, and is only used
for legacy files now. A lot of that code can therefore be removed.

First of all, the init() function was replaced by a real
constructor. A possibility to set the file extension
permissions was added.

Removed DefaultConfiguration
- TYPO3_CONF_VARS[BE][fileExtensions][ftpspace]

Removed properties:
- getUniqueNamePrefix
- tempFN
- f_ext
- mounts
- webPath
- isInit

Removed methods:
- checkPathAgainstMounts()
- findFirstWebFolder()
- slashPath()
- is_webpath()
- checkIfFullAccess()
- init()

Methods that are now protected
- is_directory()
- is_allowed()

Resolves: #77182
Releases: master
Change-Id: I2a8f40f0ea143087c23e269ef69ca4e8548b7b8f
Reviewed-on: https://review.typo3.org/45695


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>