[BUGFIX] Fix serialization of FileReference objects

FileReferences objects contain references to File
objects which itself contain service dependencies
(e.g. event dispatcher) which are not seralizable.

This leads to problems for instance when having
a multi-step form containing file uploads where
file reference objects are being serialized.

Resolves: #91196
Releases: master, 10.4
Change-Id: I7650186adc5c61528e1a1adcf06b8d6cf67a55cd
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/64841


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Oliver Hader <oliver.hader@typo3.org>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>