feat(configurations)!: flatten down, introduce meta.nix

Flatten down directory structure:
- From: `./hosts/${configuration-type}/${system}/{configuration,deploy}.nix`
-   To: `./hosts/${configuration-type}/{meta,configuration}.nix`
Keep `system` and `deploy-rs` config in `meta.nix`
Update `flake.lock`

hosts/nixos/jeeves/mindustry.nix

@@ -0,0 +1,6 @@
+{ lib, pkgs, config, ... }:
+{
+  reo101.mindustry = {
+    enable = false;
+  };
+}