[5.0.x] Fixed #35162 -- Fixed crash when adding fields with db_default on MySQL.

MySQL doesn't allow literal DEFAULT values to be used for BLOB, TEXT,
GEOMETRY or JSON columns and requires expression to be used instead.

Regression in 7414704e88.

Backport of dfc77637ea from main

tests/schema/tests.py

@@ -2306,6 +2306,19 @@ class SchemaTests(TransactionTestCase):
         columns = self.column_classes(Author)
         self.assertEqual(columns["birth_year"][1].default, "1988")
 
+    @isolate_apps("schema")
+    def test_add_text_field_with_db_default(self):
+        class Author(Model):
+            description = TextField(db_default="(missing)")
+
+            class Meta:
+                app_label = "schema"
+
+        with connection.schema_editor() as editor:
+            editor.create_model(Author)
+        columns = self.column_classes(Author)
+        self.assertIn("(missing)", columns["description"][1].default)
+
     @skipUnlessDBFeature(
         "supports_column_check_constraints", "can_introspect_check_constraints"
     )