test: gc before test-memory-usage baseline

[inoway46]

Call gc() before taking the test-memory-usage baseline so stale ArrayBuffer backing stores are cleared before the strict delta check.

This keeps the exact 10 MiB assertion while avoiding unrelated cleanup between snapshots.

Fixes: #63210

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/73302/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.03%. Comparing base (bbf51ad) to head (b83d76c).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #63214      +/-   ##
==========================================
- Coverage   90.03%   90.03%   -0.01%     
==========================================
  Files         713      713              
  Lines      224950   224950              
  Branches    42532    42537       +5     
==========================================
- Hits       202542   202535       -7     
- Misses      14175    14186      +11     
+ Partials     8233     8229       -4     

see 23 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[inoway46]

It looks like this change was not sufficient to fully fix the flaky failure.

The fedora-latest-x64 run failed on the same exact-size assertion: https://ci.nodejs.org/job/node-test-commit-linux/69926/nodes=fedora-latest-x64/

[inoway46]

Closing this since the GC-before-baseline approach still failed in CI. I'll try relaxing the arrayBuffers assertion in a separate PR.