[BUGFIX] Fetch original file from file reference in ThumbnailViewHelper

Using `treatIdAsReference` it's also possible to
pass a file reference uid to the ThumbnailViewHelper.

To allow processing such reference, the original
file is now fetched to call `process` on it.

Resolves: #102571
Releases: main, 12.4
Change-Id: If2f9cad99045d19c6dcc4b95bba6b7de71405956
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/82375


Reviewed-by: Oliver Bartsch <bo@cedev.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>