gh-152433: Windows: improve sys.getwindowsversion(), use RtlGetVersion() and allow build for UWP

[thexai]

Allow build for UWP.

Also fixes #146299

• Issue: Windows: improve compatibility to build for UWP / Xbox #152433

[thexai]

For more context, the actual issue with sys.getwindowsversion() is that return incorrect value in recent Windows 11 versions:

e.g: in Windows 11 25H2 return 10.0.26100 instead of correct 10.0.26200.

(but not directly observable because only is used as second fallback on platform module)

With this change, it will be possible use sys.getwindowsversion() as the first fallback (after WMI) and will also be compatible with UWP.

In UWP, it would be the primary method because WMI is not available and subprocess "cmd ver" is also not available.

Related to #129294

[zooba]

No thanks, we don't use ntdll from CPython.

We should be changing this function to return the version number controlled by the compatibility shims, because it will match the other compatibility behaviours that are associated with that version.

The platform module exists to get the "real" version.

[zooba]

I think we went down the "read kernel32" path because this function used to be used by platform, but that module should be fully relying on WMI now, which is more accurate (if slower, but checking the version number shouldn't be a common task, and certainly not one that's used in tight loops).