test: add describe abort signal tests

[Han5991]

Summary

Adds tests to test/parallel/test-runner-misc.js to verify AbortSignal behavior in describe blocks.
This addresses the TODO comment: // TODO(benjamingr) add more tests to describe + AbortSignal.

Changes

• Added test case for describe timeout triggering signal abort.
• Added test case for manual abort in describe.
• Verified signal propagation to nested tests.
• Updated child process output assertions to match new test results (3 cancelled tests).

Verification

• Run tools/test.py test/parallel/test-runner-misc.js

[nodejs-github-bot]

Review requested:

• @nodejs/test_runner

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.74%. Comparing base (9afa802) to head (89a9914).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #61711   +/-   ##
=======================================
  Coverage   89.74%   89.74%           
=======================================
  Files         674      674           
  Lines      204424   204424           
  Branches    39287    39287           
=======================================
+ Hits       183464   183465    +1     
- Misses      13258    13262    +4     
+ Partials     7702     7697    -5     

see 30 files with indirect coverage changes

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