[3.13] gh-144330: Initialize classmethod and staticmethod in new (GH-144498) (#144537)

[3.14] gh-144330: Initialize classmethod and staticmethod in new (GH-144498)

gh-144330: Initialize classmethod and staticmethod in new

Initialize cm_callable and sm_callable to None in classmethod and
staticmethod constructor.
(cherry picked from commit 160810de89477836f2fde7139f7ab0670399efff)

Co-authored-by: Victor Stinner <vstinner@python.org>
Co-authored-by: Aniket Singh Yadav <singhyadavaniket43@gmail.com>
Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>