[3.15] Fix Windows localhost resolution without active network

[oppnc]

Backport of #12700 to 3.15.

Cherry-pick conflict in tests/test_resolver.py resolved. All tests use AF_UNSPEC to match the real Windows failure scenario.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.24%. Comparing base (4c7dc16) to head (3d5067a).
⚠️ Report is 1 commits behind head on 3.15.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             3.15   #13086   +/-   ##
=======================================
  Coverage   98.24%   98.24%           
=======================================
  Files         135      135           
  Lines       48870    48920   +50     
  Branches     2626     2628    +2     
=======================================
+ Hits        48013    48063   +50     
  Misses        678      678           
  Partials      179      179           

Flag	Coverage Δ
CI-GHA	98.27% <100.00%> (-0.01%)	⬇️
OS-Linux	98.04% <100.00%> (-0.01%)	⬇️
OS-Windows	95.72% <100.00%> (+<0.01%)	⬆️
OS-macOS	97.25% <100.00%> (+0.01%)	⬆️
Py-3.10	97.41% <100.00%> (+<0.01%)	⬆️
Py-3.11	97.70% <100.00%> (+<0.01%)	⬆️
Py-3.12	97.79% <100.00%> (+<0.01%)	⬆️
Py-3.13	97.77% <100.00%> (+<0.01%)	⬆️
Py-3.14	97.87% <100.00%> (-0.01%)	⬇️
Py-3.14t	96.89% <100.00%> (+0.01%)	⬆️
Py-pypy-3.11	96.72% <100.00%> (-0.01%)	⬇️
VM-macos	97.25% <100.00%> (+0.01%)	⬆️
VM-ubuntu	98.04% <100.00%> (-0.01%)	⬇️
VM-windows	95.72% <100.00%> (+<0.01%)	⬆️
cython-coverage	38.43% <16.66%> (-0.03%)	⬇️

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[codspeed-hq]

Merging this PR will not alter performance

✅ 83 untouched benchmarks
⏩ 86 skipped benchmarks¹

---

_{Comparing oppnc:backport-12700-3.15 (3d5067a) with 3.15 (4a2169c)}

Footnotes

1. 86 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩