Fix Windows localhost resolution without active network

[oppnc]

What do these changes do?

Adds a Windows localhost fallback for resolver lookups that first fail with AI_ADDRCONFIG, retrying without the flag for both the threaded and async resolvers.

Are there changes in behavior for the user?

Yes. Windows users can resolve localhost while disconnected from active networks when the initial AI_ADDRCONFIG lookup fails.

Is it a substantial burden for the maintainers to support this?

No. The fallback is scoped to Windows localhost, only runs after the existing lookup fails, and is covered by resolver tests.

Related issue number

Fixes #5357

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• If you provide code modification, please add yourself to CONTRIBUTORS.txt
• Add a new news fragment into the CHANGES/ folder

Validation:

• PYTHONPATH=. AIOHTTP_NO_EXTENSIONS=1 pytest tests/test_resolver.py -q
• python -m black --check aiohttp/resolver.py tests/test_resolver.py
• python -m flake8 aiohttp/resolver.py tests/test_resolver.py

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.95%. Comparing base (7f0532c) to head (e3c05cf).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #12700   +/-   ##
=======================================
  Coverage   98.95%   98.95%           
=======================================
  Files         131      131           
  Lines       46688    46733   +45     
  Branches     2421     2423    +2     
=======================================
+ Hits        46200    46245   +45     
  Misses        366      366           
  Partials      122      122           

Flag	Coverage Δ
Autobahn	22.42% <25.00%> (-0.01%)	⬇️
CI-GHA	98.92% <100.00%> (-0.01%)	⬇️
OS-Linux	98.67% <100.00%> (-0.01%)	⬇️
OS-Windows	97.04% <100.00%> (+<0.01%)	⬆️
OS-macOS	97.93% <100.00%> (+<0.01%)	⬆️
Py-3.10	98.15% <100.00%> (+<0.01%)	⬆️
Py-3.11	98.41% <100.00%> (+<0.01%)	⬆️
Py-3.12	98.50% <100.00%> (+<0.01%)	⬆️
Py-3.13	98.47% <100.00%> (-0.01%)	⬇️
Py-3.14	98.50% <100.00%> (+<0.01%)	⬆️
Py-3.14t	97.55% <100.00%> (-0.01%)	⬇️
Py-pypy-3.11	97.42% <100.00%> (-0.01%)	⬇️
VM-macos	97.93% <100.00%> (+<0.01%)	⬆️
VM-ubuntu	98.67% <100.00%> (-0.01%)	⬇️
VM-windows	97.04% <100.00%> (+<0.01%)	⬆️
cython-coverage	37.92% <16.66%> (-0.03%)	⬇️

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[codspeed-hq]

Merging this PR will not alter performance

✅ 72 untouched benchmarks
⏩ 72 skipped benchmarks¹

---

_{Comparing oppnc:codex/fix-aiohttp-localhost-addrconfig (e3c05cf) with master (7f0532c)}

Footnotes

1. 72 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. ↩