[3.12] gh-111726: Cleanup test files after running sqlite3 doctest (GH-117604) (#117622)

Remove all temporary databases in a dedicated 'testcleanup' step
at the end of the file.
(cherry picked from commit a453f5ef9d0b89bd00488d3814c6f0a2886342b8)

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>