pkgs.formats.ini: add helper to coerce all lists more lazily

Before, we would run a mapAttrs on every attribute, checking listToValue
on each of them. But listToValue is known ahead of time. Instead, we can
only run that map if listToValue isn't null in the first place.

pkgs/pkgs-lib/formats.nix

@@ -256,6 +256,12 @@ optionalAttrs allowAliases aliases
             mapAttrs (key: val: if isList val then listToValue val else val)
           else
             id;
+        maybeCoerceAllLists =
+          listToValue:
+          if listToValue != null then
+            mapAttrs (_: mapAttrs (key: val: if isList val then listToValue val else val))
+          else
+            id;
 
         ignoredArgs = [
           "listToValue"
@@ -291,7 +297,7 @@ optionalAttrs allowAliases aliases
             generate =
               name: value:
               pipe value [
-                (mapAttrs (_: maybeCoerceList listToValue))
+                (maybeCoerceAllLists listToValue)
                 (toINI (removeAttrs args ignoredArgs))
                 (pkgs.writeText name)
               ];
@@ -343,7 +349,7 @@ optionalAttrs allowAliases aliases
               pkgs.writeText name (
                 toINIWithGlobalSection (removeAttrs args ignoredArgs) {
                   globalSection = maybeCoerceList listToValue globalSection;
-                  sections = mapAttrs (_: maybeCoerceList listToValue) sections;
+                  sections = maybeCoerceAllLists listToValue sections;
                 }
               );
           };