[3.13] gh-123811: Test that round(Decimal) can return signed zero (GH-124007) (#124048)

gh-123811: Test that round(Decimal) can return signed zero (GH-124007)
(cherry picked from commit b46c65ed2b78214cb8914779ac4e8d343ac4775e)

Co-authored-by: Sergey B Kirpichev <skirpichev@gmail.com>