Fix portable library build on Windows

[GregoryComer]

Note: This is a cherry-pick / identical copy of the existing approved PR (#13260). I inadvertently broke the ghstack when attempting to re-order the stack, leading to the old PR being merged by ghstack into the ghstack-created branch (not main).

Enable build of the portable operator library (and executor_runner, now that we have portable) on the Windows preset. There are a couple of patterns that weren't building on Windows. Both std::nan and std::signbit complain about ambiguous overload resolution when given an integer argument.

To solve the std::isnan issue, I introduced isnan_override in math_util.h, following the naming pattern from max_override / min_override / etc. in the same file. It adds a specialized branch for integers to avoid calling std::isnan. For std::signbit, I just locally specialized.

I also re-enabled optimized and quantized kernel libraries in the Windows preset, as they now build with this change.

[GregoryComer]

Stack from ghstack (oldest at bottom):

• [Windows] Run Python unit test CI on Windows #13716
• Fix remaining build issues on Windows, re-enable Windows pybind preset build CI job #13702
• ->Fix portable library build on Windows #13700

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/13700

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❌ 3 New Failures

As of commit bca23f5 with merge base 5afe90d ():

NEW FAILURES - The following jobs have failed:

• Build documentation / build (buck2) / Build doc (gh)
  At least one of the pre-conditions you specified did not hold
• pull / unittest / macos / macos-job (gh)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 5
• pull / unittest-arm-backend-with-no-fvp (test_pytest_ops) / linux-job (gh)
  RuntimeError: Command docker exec -t 32dcbc8683ef6322add04b1e9be81a3eb6a746e463d31b78307c01892d68ac02 /exec failed with exit code 1

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