Refactor imports and secrets. Add per system properties and role based secret access.

Highlights
- No need to update flake for every machine anymore, just add a properties.nix file.
- Roles are automatically generated from all machine configurations.
- Roles and their secrets automatically are grouped and show up in agenix secrets.nix
- Machines and their service configs may now query the properties of all machines.
- Machine configuration and secrets are now competely isolated into each machine's directory.
- Safety checks to ensure no mixing of luks unlocking secrets and hosts with primary ones.
- SSH pubkeys no longer centrally stored but instead per machine where the private key lies for better cleanup.

machines/ray/properties.nix

@@ -0,0 +1,22 @@
+{
+  hostNames = [
+    "ray"
+  ];
+
+  arch = "x86_64-linux";
+
+  systemRoles = [
+    "personal"
+    "deploy"
+  ];
+
+  hostKey = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIDQM8hwKRgl8cZj7UVYATSLYu4LhG7I0WFJ9m2iWowiB";
+
+  userKeys = [
+    "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIFeTK1iARlNIKP/DS8/ObBm9yUM/3L1Ub4XI5A2r9OzP"
+  ];
+
+  deployKeys = [
+    "sk-ssh-ed25519@openssh.com AAAAGnNrLXNzaC1lZDI1NTE5QG9wZW5zc2guY29tAAAAIEaGIwLiUa6wQLlEF+keQOIYy/tCmJvV6eENzUQjSqW2AAAABHNzaDo="
+  ];
+}