Pin GitHub Actions to full-length commit SHAs - #299

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@0717577d45739eb3c851188b29f50ed6c0b2194e, actions/setup-java@cf277c60eb25467037889841efdb72551f06f6c3, actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02, gradle/gradle-build-action@a8f75513eafdebd8141bd1cd4e30fcd194af8dfa. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Failed to restore v8-gradle|Linux|build validation-build[37a6259cc0c1dae299a7866489dff0bd]-61d6aaa9a69e96d1a38c175f92b4cfbf146b3f7a: Error: Cache service responded with 400