Previously, we would move entries each time they were pasted. Thus, if
you were to cut some files and pasted them in folder `a` and then `b`,
they would only occur in folder `b` and not in folder `a`. This is
unintuitive - e.g. the same does not apply to text and does not happen
in other editors.

This PR improves this behavior - after the first paste of a cut
clipboard, we change the clipboard to a copy clipboard, ensuring that
for all folloing pastes, the entries are not moved again. In the above
example, the files would then also be found in folder `a`. This is also
reflected in the added test.

Release Notes:

- Ensured that cut project panel entries are cut-pasted only on the
first use, and copy-pasted on all subsequent pastes.