nix: reorganize

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>

flake.lock

@@ -39,6 +39,24 @@
         "type": "github"
       }
     },
+    "flake-parts": {
+      "inputs": {
+        "nixpkgs-lib": "nixpkgs-lib"
+      },
+      "locked": {
+        "lastModified": 1690933134,
+        "narHash": "sha256-ab989mN63fQZBFrkk4Q8bYxQCktuHmBIBqUG1jl6/FQ=",
+        "owner": "hercules-ci",
+        "repo": "flake-parts",
+        "rev": "59cf3f1447cfc75087e7273b04b31e689a8599fb",
+        "type": "github"
+      },
+      "original": {
+        "owner": "hercules-ci",
+        "repo": "flake-parts",
+        "type": "github"
+      }
+    },
     "flake-utils": {
       "inputs": {
         "systems": "systems"
@@ -91,12 +109,30 @@
         "type": "github"
       }
     },
+    "nixpkgs-lib": {
+      "locked": {
+        "dir": "lib",
+        "lastModified": 1690881714,
+        "narHash": "sha256-h/nXluEqdiQHs1oSgkOOWF+j8gcJMWhwnZ9PFabN6q0=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "9e1960bc196baf6881340d53dccb203a951745a2",
+        "type": "github"
+      },
+      "original": {
+        "dir": "lib",
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
     "root": {
       "inputs": {
         "crane": "crane",
+        "flake-parts": "flake-parts",
         "nixpkgs": "nixpkgs",
-        "rust-overlay": "rust-overlay_2",
-        "utils": "utils"
+        "rust-overlay": "rust-overlay_2"
       }
     },
     "rust-overlay": {
@@ -174,39 +210,6 @@
         "repo": "default",
         "type": "github"
       }
-    },
-    "systems_3": {
-      "locked": {
-        "lastModified": 1681028828,
-        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
-        "owner": "nix-systems",
-        "repo": "default",
-        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
-        "type": "github"
-      },
-      "original": {
-        "owner": "nix-systems",
-        "repo": "default",
-        "type": "github"
-      }
-    },
-    "utils": {
-      "inputs": {
-        "systems": "systems_3"
-      },
-      "locked": {
-        "lastModified": 1689068808,
-        "narHash": "sha256-6ixXo3wt24N/melDWjq70UuHQLxGV8jZvooRanIHXw0=",
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "rev": "919d646de7be200f3bf08cb76ae1f09402b6f9b4",
-        "type": "github"
-      },
-      "original": {
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "type": "github"
-      }
     }
   },
   "root": "root",