use explicit module value on forward

this allows imports to not be mistaken for an config value

checkmate/modules/tests/forward.nix

···
 
       targetSubmodule = {
         options.targetMod = lib.mkOption {
-          type = lib.types.submoduleWith {
-            modules = [
-              {
-                options.names = lib.mkOption {
-                  type = lib.types.listOf lib.types.str;
-                };
-              }
-            ];
+          type = lib.types.submodule {
+            options.names = lib.mkOption {
+              type = lib.types.listOf lib.types.str;
+            };
           };
         };
       };

nix/forward.nix

···
       path = intoPath item;
       aspect = fromAspect item;
       module = aspect.resolve { class = from; };
-      config = lib.setAttrByPath path { imports = [ module ]; };
+      config = lib.setAttrByPath path (
+        { ... }:
+        {
+          imports = [ module ];
+        }
+      );
     in
     {
       ${into} = config;