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 a08b3a4d19.tar.gz \
      --argstr baseRev 57b193d8dd
    result/bin/apply-formatting $NIXPKGS_PATH

nixos/modules/system/boot/kernel_config.nix

@@ -2,15 +2,24 @@
 
 with lib;
 let
-  mergeFalseByDefault = locs: defs:
-    if defs == [] then abort "This case should never happen."
-    else if any (x: x == false) (getValues defs) then false
-    else true;
+  mergeFalseByDefault =
+    locs: defs:
+    if defs == [ ] then
+      abort "This case should never happen."
+    else if any (x: x == false) (getValues defs) then
+      false
+    else
+      true;
 
   kernelItem = types.submodule {
     options = {
       tristate = mkOption {
-        type = types.enum [ "y" "m" "n" null ];
+        type = types.enum [
+          "y"
+          "m"
+          "n"
+          null
+        ];
         default = null;
         internal = true;
         visible = true;
@@ -31,7 +40,9 @@ let
       };
 
       optional = mkOption {
-        type = types.bool // { merge = mergeFalseByDefault; };
+        type = types.bool // {
+          merge = mergeFalseByDefault;
+        };
         default = false;
         description = ''
           Whether option should generate a failure when unused.
@@ -41,17 +52,36 @@ let
     };
   };
 
-  mkValue = with lib; val:
-  let
-    isNumber = c: elem c ["0" "1" "2" "3" "4" "5" "6" "7" "8" "9"];
-
-  in
-    if (val == "") then "\"\""
-    else if val == "y" || val == "m" || val == "n" then val
-    else if all isNumber (stringToCharacters val) then val
-    else if substring 0 2 val == "0x" then val
-    else val; # FIXME: fix quoting one day
+  mkValue =
+    with lib;
+    val:
+    let
+      isNumber =
+        c:
+        elem c [
+          "0"
+          "1"
+          "2"
+          "3"
+          "4"
+          "5"
+          "6"
+          "7"
+          "8"
+          "9"
+        ];
 
+    in
+    if (val == "") then
+      "\"\""
+    else if val == "y" || val == "m" || val == "n" then
+      val
+    else if all isNumber (stringToCharacters val) then
+      val
+    else if substring 0 2 val == "0x" then
+      val
+    else
+      val; # FIXME: fix quoting one day
 
   # generate nix intermediate kernel config file of the form
   #
@@ -64,19 +94,21 @@ let
   # returns a string, expr should be an attribute set
   # Use mkValuePreprocess to preprocess option values, aka mark 'modules' as 'yes' or vice-versa
   # use the identity if you don't want to override the configured values
-  generateNixKConf = exprs:
-  let
-    mkConfigLine = key: item:
-      let
-        val = if item.freeform != null then item.freeform else item.tristate;
-      in
-        optionalString (val != null)
-            (if (item.optional)
-            then "${key}? ${mkValue val}\n"
-            else "${key} ${mkValue val}\n");
+  generateNixKConf =
+    exprs:
+    let
+      mkConfigLine =
+        key: item:
+        let
+          val = if item.freeform != null then item.freeform else item.tristate;
+        in
+        optionalString (val != null) (
+          if (item.optional) then "${key}? ${mkValue val}\n" else "${key} ${mkValue val}\n"
+        );
 
-    mkConf = cfg: concatStrings (mapAttrsToList mkConfigLine cfg);
-  in mkConf exprs;
+      mkConf = cfg: concatStrings (mapAttrsToList mkConfigLine cfg);
+    in
+    mkConf exprs;
 
 in
 {
@@ -99,11 +131,12 @@ in
 
     settings = mkOption {
       type = types.attrsOf kernelItem;
-      example = literalExpression '' with lib.kernel; {
-        "9P_NET" = yes;
-        USB = option yes;
-        MMC_BLOCK_MINORS = freeform "32";
-      }'';
+      example = literalExpression ''
+        with lib.kernel; {
+               "9P_NET" = yes;
+               USB = option yes;
+               MMC_BLOCK_MINORS = freeform "32";
+             }'';
       description = ''
         Structured kernel configuration.
       '';