[BUGFIX] Fix copying folders in filelist

Internally, the clipboard class only knows of the identifier
"_FILE", which is used for copying both files and folders.

Resolves: #100367
Releases: main
Change-Id: Ibef87567cd71f73d2e4b3c8a360b1bff1f420fd0
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78340


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