lib.types.deferredModule: Allow path-typed module references

lib/tests/modules/deferred-module.nix

···
 
     {
       _file = "default-a-is-b.nix";
-      default = { config, ... }: {
-        settingsDict.a = config.settingsDict.b;
-      };
+      default = ./define-settingsDict-a-is-b.nix;
     }
 
     {

lib/tests/modules/define-settingsDict-a-is-b.nix

···
+{ config, ... }: {
+  settingsDict.a = config.settingsDict.b;
+}

lib/types.nix

···
     deferredModule = mkOptionType {
       name = "deferredModule";
       description = "module";
-      check = t: isAttrs t || isFunction t;
+      check = x: isAttrs x || isFunction x || path.check x;
       merge = loc: defs: map (def: lib.setDefaultModuleLocation "${def.file}, via option ${showOption loc}" def.value) defs;
     };