Add tests for msvcrt module

[aisk]

Bug report

Bug description:

msvcrt is a public module, but it has no tests.

Linked PRs

• gh-108996: add tests for msvcrt #109004
• gh-108996: Skip broken test_msvcrt for now #109169
• gh-108996: fix and enable test_msvcrt #109226

[terryjreedy]

Thanks for the submission. I reviewed the PR but would like someone else to look at the file op class.