refactor(tazjin/nixos): Split up desktop/laptop configurations

Change-Id: I0f5d631491be0c811ad171510568aac097d2fddd
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5553
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: tazjin <tazjin@tvl.su>

users/tazjin/nixos/modules/laptop.nix

@@ -0,0 +1,12 @@
+# Configuration specifically for laptops that move around.
+{ ... }:
+
+{
+  # Automatically detect location to use for redshift
+  location.provider = "geoclue2";
+
+  # Enable power-saving features.
+  services.tlp.enable = true;
+
+  programs.light.enable = true;
+}