[3.12] gh-113009: Fix multiprocessing Process.terminate() on Windows (GH-113128)...

[3.12] gh-113009: Fix multiprocessing Process.terminate() on Windows (GH-113128) (#113177)

gh-113009: Fix multiprocessing Process.terminate() on Windows (GH-113128)

On Windows, Process.terminate() no longer sets the returncode
attribute to always call WaitForSingleObject() in Process.wait().
Previously, sometimes the process was still running after
TerminateProcess() even if GetExitCodeProcess() is not STILL_ACTIVE.
(cherry picked from commit 4026ad5b2c595b855a3605420cfa0e3d49e63db7)

Co-authored-by: Victor Stinner <vstinner@python.org>