Update and pin GitHub Actions; stop testing EOL Python 3.7-3.9 in CI

[anoadragon453]

Updates the old GitHub Actions in use in this repository, and pins them to a specific hash.

We also drop testing the end-of-life Python versions 3.7-3.9 in CI. This allows CI to pass again. Note: This PR does not officially drop support for these Python versions.** Doing so requires updating setup.cfg. Let's do that in a separate PR ⏩

Finally, we add the zizmor Github Action so we prevent introducing any regressions in the security of our GitHub Actions.

[github-advanced-security]

You are seeing this message because GitHub Code Scanning has recently been set up for this repository, or this pull request contains the workflow file for the Code Scanning tool.

What Enabling Code Scanning Means:

• The 'Security' tab will display more code scanning analysis results (e.g., for the default branch).
• Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results.
• You will be able to see the analysis results for the pull request's branch on this overview once the scans have completed and the checks have passed.

For more information about GitHub Code Scanning, check out the documentation.