[3.14] gh-145633: Fix struct.pack('f') on s390x (GH-146422) (#146460)

gh-145633: Fix struct.pack('f') on s390x (GH-146422)

Use PyFloat_Pack4() to raise OverflowError.
Add more tests on packing/unpacking floats.
(cherry picked from commit 8de70b31c59b1d572d95f8bb471a09cfe4cd2b13)

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