Migrate Terraform definitions to Terranix

[matthewmazzanti]

Terranix allows for Terraform definitions in nix: https://terranix.org/
This would allow more definitions in nix, interesting things like shared hostnames/drive names, and pulling the AMI from nixpkgs here

One risk here is that we have a lot of Terraform references, which we use a lot of, are a bit ugly: https://terranix.org/documentation/terranix-vs-hcl/#references