Fixed #28549 -- Fixed QuerySet.defer() with super and subclass fields.

Previously, deferring fields in different classes didn't omit the
superclass' deferred field.

Thanks Simon Charette for the suggested fix.

django/db/models/sql/query.py

@@ -649,7 +649,7 @@ class Query:
             # models.
             workset = {}
             for model, values in seen.items():
-                for field in model._meta.fields:
+                for field in model._meta.local_fields:
                     if field in values:
                         continue
                     m = field.model._meta.concrete_model

tests/defer/tests.py

@@ -188,6 +188,11 @@ class BigChildDeferTests(AssertionMixin, TestCase):
         self.assertEqual(obj.value, "foo")
         self.assertEqual(obj.other, "bar")
 
+    def test_defer_subclass_both(self):
+        # Deferring fields from both superclass and subclass works.
+        obj = BigChild.objects.defer("other", "value").get(name="b1")
+        self.assert_delayed(obj, 2)
+
     def test_only_baseclass_when_subclass_has_added_field(self):
         # You can retrieve a single field on a baseclass
         obj = BigChild.objects.only("name").get(name="b1")