test_runner: add handleSignals option to run()

[mete0rfish]

Implements the TODO from #43977

---

The built-in test runner already handles SIGINT and SIGTERM, marking any running tests as interrupted before exiting. The run() API, however, did not provide a way to enable the same behavior.

This change adds an opt-in handleSignals option for test runner integrations:

run({files: ['test.js'],handleSignals: true,});

Signal handling remains disabled by default, so existing run() users that manage process signals themselves are unaffected. Custom runners can now opt in when they need behavior consistent with the CLI test runner.

[nodejs-github-bot]

Review requested:

• @nodejs/test_runner

[codecov]

Codecov Report

❌ Patch coverage is 82.35294% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.27%. Comparing base (e6a8d06) to head (0bfc0f9).
⚠️ Report is 379 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/internal/test_runner/harness.js	75.00%	3 Missing ⚠️

Additional details and impacted files

@@ Coverage Diff @@## main #64357 +/- ##
==========================================
- Coverage 92.01% 90.27% -1.75% 
==========================================
Files 379 741 +362 Lines 166972 241004 +74032 Branches 25554 45422 +19868 ==========================================
+ Hits 153639 217558 +63919 - Misses 13041 15018 +1977 - Partials 292 8428 +8136 

Files with missing lines	Coverage Δ
lib/internal/test_runner/runner.js	94.45% <100.00%> (+0.39%)	⬆️
lib/internal/test_runner/harness.js	93.10% <75.00%> (+4.97%)	⬆️

... and 548 files with indirect coverage changes

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