More TF fixes (#28081)

* More build_in_name_scope()

* Make sure we set the save spec now we don't do it with dummies anymore

* make fixup

tests/utils/test_modeling_tf_core.py

@@ -217,7 +217,7 @@ class TFCoreModelTesterMixin:
         for model_class in self.all_model_classes[:2]:
             class_inputs_dict = self._prepare_for_class(inputs_dict, model_class)
             model = model_class(config)
-            model.build()
+            model.build_in_name_scope()
             num_out = len(model(class_inputs_dict))
 
             for key in list(class_inputs_dict.keys()):