What does this PR do?

This PR adds support for managing packages using the nix package manager.

New Behavior

Now you can install, update or remove packages using the nix package manager.

Merge requirements satisfied?

• Docs
• Changelog - https://docs.saltproject.io/en/master/topics/development/changelog.html
• Tests written/updated

Commits signed with GPG?

Yes

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Please address the pre-commit failures. Maybe just need to rebase.

Apparently, the branch is up-to-date... But the issue does not seem to be related to my changes.

It's an issue installing cassandra-driver. May be the host machine where the CI is running has changed its packages?

Well, once things are passing on the nightly builds for the master branch, then rebase this.