Added moveToTrashDuplicateName() to see what happens if you attempt to
trash two files with the same exact full path. Both files should get
independently moved to the trash bin and not clobber each other.
Added moveToTrashXdgSafety() to test that QFileSystemEngine will
properly skip over an unsafe $root/.Trash directory, as required by the
XDG specification. I think the specification should also make security
requirements on $root/.Trash-$uid too, but that's for another change.
Pick-to: 6.6
Change-Id: I9d43e5b91eb142d6945cfffd1786cd60e4244c7c
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>