Fixed #36173 -- Stabilized identity of Concat with an explicit output_field.

When Expression.__init__() overrides make use of *args, **kwargs
captures their argument values are respectively bound as a tuple and
dict instances. These composite values might themselves contain values
that require special identity treatments such as Concat(output_field)
as it's a Field instance.

Refs #30628 which introduced bound Field differentiation but lacked
argument captures handling.

Thanks erchenstein for the report.

tests/db_functions/text/test_concat.py

@@ -107,3 +107,17 @@ class ConcatTests(TestCase):
             ctx.captured_queries[0]["sql"].count("::text"),
             1 if connection.vendor == "postgresql" else 0,
         )
+
+    def test_equal(self):
+        self.assertEqual(
+            Concat("foo", "bar", output_field=TextField()),
+            Concat("foo", "bar", output_field=TextField()),
+        )
+        self.assertNotEqual(
+            Concat("foo", "bar", output_field=TextField()),
+            Concat("foo", "bar", output_field=CharField()),
+        )
+        self.assertNotEqual(
+            Concat("foo", "bar", output_field=TextField()),
+            Concat("bar", "foo", output_field=TextField()),
+        )