child_process: keep SIGWINCH from killing on Win

[PickBas]

child_process: keep SIGWINCH from killing on Win

On Windows, ProcessWrap::Kill coerced any signal outside {SIGKILL, SIGTERM, SIGINT, SIGQUIT, 0} to SIGKILL. This wrongly terminated a process on kill('SIGWINCH'), a non-terminal signal.

SIGWINCH now skips the coercion and reaches libuv, which returns UV_ENOSYS, surfaced as an ENOSYS error in JS, leaving the target process alive.

Fixes: #64324

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.24%. Comparing base (4140d4c) to head (9d89021).
⚠️ Report is 44 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #64510      +/-   ##
==========================================
- Coverage   90.25%   90.24%   -0.02%     
==========================================
  Files         741      739       -2     
  Lines      241216   241669     +453     
  Branches    45442    45548     +106     
==========================================
+ Hits       217713   218093     +380     
- Misses      15079    15110      +31     
- Partials     8424     8466      +42     

Files with missing lines	Coverage Δ
src/process_wrap.cc	75.00% <ø> (ø)

... and 63 files with indirect coverage changes

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