GH Actions: mass update of action versions

[clebergnu]

According to GH, we must update the version of used actions due to deprecations of Node.js 16. Message given is:

Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: actions/checkout@v3, actions/setup-python@v4, actions/upload-artifact@v3.

Reference: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/