Move nixUnstable to base layer

layers/base.nix

@@ -21,6 +21,11 @@ in
     ./ioschedulers.nix
   ];
 
+  nix.package = pkgs.nixUnstable;
+  nix.extraOptions = ''
+    experimental-features = nix-command flakes
+  '';
+
   # This value determines the NixOS release with which your system is to be
   # compatible, in order to avoid breaking some software such as database
   # servers. You should change this only after NixOS release notes say you

layers/workstation.nix

@@ -6,11 +6,6 @@
     #./vscode.nix
   ];
 
-  nix.package = pkgs.nixUnstable;
-  nix.extraOptions = ''
-    experimental-features = nix-command flakes
-  '';
-
   documentation.dev.enable = true;
 
   environment.systemPackages = with pkgs; [