Update GHA workflows and actions

[ziegenberg]

The updates are mostly about the deprecation of Node 20 on GitHub Actions runners: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.27%. Comparing base (80cb977) to head (2a6dd19).

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #235   +/-   ##
=========================================
  Coverage     98.27%   98.27%           
  Complexity      994      994           
=========================================
  Files            42       42           
  Lines          2961     2961           
=========================================
  Hits           2910     2910           
  Misses           51       51           

☔ View full report in Codecov by Harness.
📢 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.