Remove Windows 7 specific code

[maxbachmann]

Feature or enhancement

There are still a couple of code sections special handling Windows 7. Removing at least part of those is required for #102255. So we might as well go ahead and clean up a large part of those.

Linked PRs

• gh-102336: remove windows 7 special handling #102337
• gh-102336: Ensure CancelIoEx result is not ignored #102347