Restore runs-on: windows-latest

[rwgk]

Description

1. Revert PR s/windows-latest/windows-2022/ in .github/workflows/{ci,pip}.yml #5826
2. Add module-level skip for Windows build >= 26100 in test_iostream.py

Suggested changelog entry:

• Placeholder.

[henryiii]

Not following closely, do we know why we have to skip for builds of windows above that value?

[rwgk]

Not following closely, do we know why we have to skip for builds of windows above that value?

Sorry I don't, at all. I hope someone else will pick this up.

I stumbled over this while working on #5796 (comment)

When I saw the test_iostream.py failures on my workstation, I was guessing they might be identical to what we saw in the CI with windows-latest aka windows-2025. Then I asked ChatGPT how we could detect windows-2025 or Windows 11 24H2 (my workstation), and it instantly gave me the Windows build number to look for.

Bottom line: This PR doesn't fix anything, but

• it narrows down where the problem is,
• allows us to continue using windows-latest in the CI for everything else, and
• eliminates the distracting errors when running the unit tests locally on my workstation.

[henryiii]

Suggested change

	ifsys.platform=="win32":
	ifsys.platform.startswith("win32"):

It's canonical to use startswith when checking sys.platform, though it's often not required.

[rwgk]

Looking at this with a fresh eye: For a moment I forgot that we have env.WIN. Changed to use that: commit 8b79a85

[henryiii]

Suggested change

	" Skipping iostream capture (redirection regression under investigation)",
	" Skipping iostream capture (redirection regression needs investigation)",

[rwgk]

Done: commit 8b79a85

[rwgk]

Thanks @henryiii!