LPS-40926 Use DLApp for deleting the entities in SMDHs

Hey Alex,

This is the change to use the DLApp in the FileEntry and FolderStagedModelDataHandlers.

Before we have started to rewrite the whole staging environment we have used the FileEntryUtil and FolderUtil so I've figured to use it in the delete as well.

Otherwise the DLApp is being used to delete the entities where the related stuff is being deleted as well.

Thanks,

Máté