test: prefer major GC in cppgc-object

[Han5991]

Summary

• In test/addons/cppgc-object/test.js, force each gcUntil() loop to request a major GC
  ({ type: 'major', execution: 'beforeUserJS' }). This increases the likelihood that old
  CppGCed wrappers are collected promptly.

• The test logic remains the same; it just invokes a stronger GC flavor to avoid the CI
  flake where “All old CppGCed are destroyed” never becomes true within 10 attempts.

• https://github.com/nodejs/node/actions/runs/19245913659/job/55019892774?pr=60665

  Testing

  • make build-addons
  • python3 tools/test.py addons/cppgc-object/test

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.55%. Comparing base (4f1ab8c) to head (e0cd646).
⚠️ Report is 17 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #60672      +/-   ##
==========================================
+ Coverage   88.03%   88.55%   +0.52%     
==========================================
  Files         703      703              
  Lines      208257   208257              
  Branches    40069    40156      +87     
==========================================
+ Hits       183336   184420    +1084     
+ Misses      16883    15866    -1017     
+ Partials     8038     7971      -67     

see 104 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/70224/

[Han5991]

@legendecas

Hi, this CI failure looks unrelated to the changes in this PR and seems to be caused by a flaky test.
Could you re-run only the failed CI jobs when you get a chance?

Thanks!