[3.14] gh-116738: Statically initialize special constants in cmath module (gh-142161) (gh-142261)

The initialization during `mod_exec` wasn't thread-safe with multiple interpreters.
(cherry picked from commit 2dac9e6016c81abbefa4256253ff5c59b29378a7)

Co-authored-by: Alper <alperyoney@fb.com>