[3.13] gh-118761: Improve import time of `subprocess` (GH-129427) (#129447)

gh-118761: Improve import time of `subprocess` (GH-129427)

* subprocess: lazy import signal and locale to improve module import time
(cherry picked from commit 49f24650e4541456872490ec2b59d6d186204891)

Co-authored-by: Taneli Hukkinen <3275109+hukkin@users.noreply.github.com>