Add more tests for `getpass`

[donbarbos]

This is something I thought of when working #130496, I noticed that some tests were missing.
Test Lib/test/test_getpass.py only has three classes: GetpassGetuserTest, GetpassRawinputTest, UnixGetpassTest.

This clearly doesn't cover all cases, I think we should add at least WinGetpassTest and check that both implementations (unix_getpass and win_getpass) work the same.

Linked PRs

• gh-130524 Create WinGetpassTest class for improved coverage #130529

[tomasr8]

Just an FYI, the devguide has some information on how to systematically measure and increase test coverage: https://devguide.python.org/testing/coverage/

[floor-licker]

Can I work on this?

[donbarbos]

Can I work on this?

yeah, i think so