Reduce the number of CI jobs when checking for discrepancies, increase consistency with missing installations check, add support for 2026.06 everywhere - #1576

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/