[!!!][TASK] Add property types to FileLinkHandler

Doing so also allows for a bit of code cleanup.

Used command:

> ./Build/Scripts/runTests.sh -s phpstanGenerateBaseline

Resolves: #97982
Releases: main
Change-Id: Id351fda2040fd7de3931a109b77ff0c947c552b3
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/75251


Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>