[3.12] gh-123811: test that round() can return signed zero (GH-123829) (#123939)

gh-123811: test that round() can return signed zero (GH-123829)
(cherry picked from commit d2b9b6f919e92184420c8e13d078e83447ce7917)

Co-authored-by: Sergey B Kirpichev <skirpichev@gmail.com>
Co-authored-by: Victor Stinner <vstinner@python.org>