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