[TASK] Check and use current file hash and size on export

On creating exports the file hash and size is used from the
sys_file table. Since this could be not up-to-date in real live
projects, those files fail to be imported.

To prevent this, use the correct data for the export and show
an error to the user.

Resolves: #58761
Releases: 6.2
Change-Id: I7aacc6f00c52bc01c753af4ee32202a9219c02a1
Reviewed-on: https://review.typo3.org/30061
Reviewed-by: Bernd Niehues
Tested-by: Bernd Niehues
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters