test_runner: preserve AssertionError actual constructor name across isolation

[inoway46]

Summary

This PR fixes the regression described in #50397 where test runner output can lose the original constructor name for AssertionError values (for example, ExtendedArray being shown as plain Array in actual output).

What changed

1. Added a regression test first

   • test/parallel/test-runner-issue-50397.js
   • test/fixtures/test-runner/issue-50397/prototype-mismatch.js
   • Covers both --test-isolation=none and --test-isolation=process.

2. Implemented a test-runner-scoped fix

   • Added lib/internal/test_runner/assertion_error_prototype.js to collect/apply metadata for AssertionError actual/expected constructor names.
   • Wired metadata collection in lib/internal/test_runner/reporter/v8-serializer.js.
   • Wired metadata application and cleanup in lib/internal/test_runner/runner.js.

3. Added focused sequential coverage for the helper logic

   • test/sequential/test-runner-assertion-error-prototype.js
   • Verifies metadata collection, restoration after serialize/deserialize, and idempotent application.

Why this approach

The fix is intentionally scoped to internal/test_runner/* so that shared internal/error_serdes behavior is unchanged for other subsystems.

Tests

• python3 tools/test.py test/parallel/test-runner-issue-50397.js
• python3 tools/test.py test/sequential/test-runner-assertion-error-prototype.js
• python3 tools/test.py test/sequential/test-error-serdes.js

Fixes #50397

[nodejs-github-bot]

Review requested:

• @nodejs/test_runner

[MoLow]

@BridgeAR PTAL

[codecov]

Codecov Report

❌ Patch coverage is 81.48148% with 40 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.74%. Comparing base (f6464c5) to head (0fee869).
⚠️ Report is 59 commits behind head on main.

Files with missing lines	Patch %	Lines
.../internal/test_runner/assertion_error_prototype.js	79.78%	33 Missing and 5 partials ⚠️
lib/internal/test_runner/runner.js	84.61%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #61716      +/-   ##
==========================================
- Coverage   89.76%   89.74%   -0.03%     
==========================================
  Files         673      676       +3     
  Lines      203944   204718     +774     
  Branches    39191    39352     +161     
==========================================
+ Hits       183080   183720     +640     
- Misses      13194    13272      +78     
- Partials     7670     7726      +56     

Files with missing lines	Coverage Δ
lib/internal/test_runner/reporter/v8-serializer.js	100.00% <100.00%> (ø)
lib/internal/test_runner/runner.js	92.91% <84.61%> (-0.21%)	⬇️
.../internal/test_runner/assertion_error_prototype.js	79.78% <79.78%> (ø)

... and 59 files with indirect coverage changes

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