[BUGFIX] Respect user mount points within FormPersistenceManager

Let the FormPersistenceManager respect user mount points and
auto created file mounts while retrieving and creating folders
which are configured within
"TYPO3.CMS.Form.persistenceManager.allowedFileMounts".

Resolves: #88895
Releases: master, 9.5
Change-Id: Ic422c692e268165de986e43239d9f293a71e0b25
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/62415


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Mathias Brodala <mbrodala@pagemachine.de>
Tested-by: Björn Jacob <bjoern.jacob@tritum.de>
Tested-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>
Reviewed-by: Mathias Brodala <mbrodala@pagemachine.de>
Reviewed-by: Björn Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>