Those resources are related to back-end infrastructure (servers, etc). Garuda doesn't ship any user-space tools related to Nix.
Edit: Those files are not related to the Nix server infrastructure after all, rather they are related to a testing/work-in-progess project.
If you would like to use the Nix package manager on a Garuda system, you can set that up according to these instructions:
hopefully one day we can have a garuda nix distro!