treewide: format all inactive Nix files

After final improvements to the official formatter implementation,
this commit now performs the first treewide reformat of Nix files using it.
This is part of the implementation of RFC 166.

Only "inactive" files are reformatted, meaning only files that
aren't being touched by any PR with activity in the past 2 months.
This is to avoid conflicts for PRs that might soon be merged.
Later we can do a full treewide reformat to get the rest,
which should not cause as many conflicts.

A CI check has already been running for some time to ensure that new and
already-formatted files are formatted, so the files being reformatted here
should also stay formatted.

This commit was automatically created and can be verified using

    nix-build https://github.com/infinisil/treewide-nixpkgs-reformat-script/archive/a08b3a4d199c6124ac5b36a889d9099b4383463f.tar.gz \
      --argstr baseRev b32a094368
    result/bin/apply-formatting $NIXPKGS_PATH

nixos/modules/config/xdg/icons.nix

@@ -1,4 +1,9 @@
-{ config, lib, pkgs, ... }:
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
 {
   meta = {
     maintainers = lib.teams.freedesktop.members;
@@ -15,7 +20,7 @@
     };
     xdg.icons.fallbackCursorThemes = lib.mkOption {
       type = lib.types.listOf lib.types.str;
-      default = [];
+      default = [ ];
       description = ''
         Names of the fallback cursor themes, in order of preference, to be used when no other icon source can be found.
         Set to `[]` to disable the fallback entirely.
@@ -29,20 +34,22 @@
       "/share/pixmaps"
     ];
 
-    environment.systemPackages = [
-      # Empty icon theme that contains index.theme file describing directories
-      # where toolkits should look for icons installed by apps.
-      pkgs.hicolor-icon-theme
-    ] ++ lib.optionals (config.xdg.icons.fallbackCursorThemes != []) [
-      (pkgs.writeTextFile {
-        name = "fallback-cursor-theme";
-        text = ''
-          [Icon Theme]
-          Inherits=${lib.concatStringsSep "," config.xdg.icons.fallbackCursorThemes}
-        '';
-        destination = "/share/icons/default/index.theme";
-      })
-    ];
+    environment.systemPackages =
+      [
+        # Empty icon theme that contains index.theme file describing directories
+        # where toolkits should look for icons installed by apps.
+        pkgs.hicolor-icon-theme
+      ]
+      ++ lib.optionals (config.xdg.icons.fallbackCursorThemes != [ ]) [
+        (pkgs.writeTextFile {
+          name = "fallback-cursor-theme";
+          text = ''
+            [Icon Theme]
+            Inherits=${lib.concatStringsSep "," config.xdg.icons.fallbackCursorThemes}
+          '';
+          destination = "/share/icons/default/index.theme";
+        })
+      ];
 
     # libXcursor looks for cursors in XCURSOR_PATH
     # it mostly follows the spec for icons