Pin GitHub Actions to full-length commit SHAs - #426

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@11d5960a326750d5838078e36cf38b85af677262, actions/setup-java@cf277c60eb25467037889841efdb72551f06f6c3, actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020, coactions/setup-xvfb@b6b4fcfb9f5a895edadc3bc76318fae0ac17c8b3. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/