[3.12] gh-111881: Use lazy import in test.support (#111885) (#111890)

gh-111881: Use lazy import in test.support (#111885)

* Import lazily getpass in test.support
* Only import ctypes on Windows in test.support.os_helper.

(cherry picked from commit 0372e3b02a7e3dc1c564dba94dcd817c5472b04f)