bpo-19072: Classmethod can wrap other classmethod like descriptors (GH-29634) (GH-29643)

staticmethod() also became callable in Python 3.10.

See: b83861f02.
(cherry picked from commit e34809e1c2a09478f4e0651d551c9c12d3c556ab)

Co-authored-by: Raymond Hettinger <rhettinger@users.noreply.github.com>