chore: use projen primitives for artifact actions in GHA Workflows

[mrgrain]

Replaces all hardcoded actions/upload-artifact@v4.4.0 and actions/download-artifact@v4 references with projen's WorkflowSteps.uploadArtifact() and WorkflowSteps.downloadArtifact() primitives. This upgrades to v7 and v8 respectively, resolving the Node.js 20 deprecation warnings that were firing on the release and integ workflows.

Checklist

• This change contains a major version upgrade for a dependency and I confirm all breaking changes are addressed
  • Release notes for the new version:

---

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Scanned Files

• .github/workflows/release.yml

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.10%. Comparing base (82a8a3c) to head (aeaabd4).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1489   +/-   ##
=======================================
  Coverage   88.10%   88.10%           
=======================================
  Files          74       74           
  Lines       10669    10669           
  Branches     1457     1457           
=======================================
  Hits         9400     9400           
  Misses       1241     1241           
  Partials       28       28           

Flag	Coverage Δ
suite.unit	88.10% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 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.