Fix windows file limit check

[rpeden]

Prefect 2.10.17 added a Unix only import in utilities/filesystem.py that breaks when running Prefect server or an agent on Windows.

Credit to @grenzi for suggesting a solution to this; this PR only differs from their PR #10055 in calling getmaxstdio without adding a dependency on pywin32.

This PR calls a function in the Windows Universal C runtime to perform the same check on Windows, and scopes the resource module import to ensure it won't run on Windows. Using ctypes in this instance should be safe, as Microsoft is unlikely to remove the Universal C runtime DLL from Windows given how many of their own applications depend on it.

See https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/getmaxstdio for more detail.

Closes #10054
Closes #10058

Although this PR adds a test for get_open_file_limit, many other tests in tests/utilities/test_filesystem.py fail on Windows due to hardcoded Unix file paths. In case it is useful, I opened a draft PR (#10065) with a potential solution that makes the failing tests work cross-platform.

Example

Before: run prefect server start on Windows and get an error: ImportError: No module named 'resource'
After: prefect server start works as expected.

The same applies for the prefect agent start command.

Checklist

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[grenzi]

@rpeden It's been many a year since i've been in the OS level api calls.

This is great. Avoids a dependency, and uses os.name which is, from my googling the differences here on a sat morning, probably a simpler alternative. (also, today i learned about Jython, which causes os.name to return 'java' - what an odd beast it is)

Anyway, I closed my PR and referenced here since this is a better solution. Thanks!

[desertaxle]

LGTM! Thanks @rpeden!