feat: add global max row limit (#16683)

* feat: add global max limit

* fix lint and tests

* leave SAMPLES_ROW_LIMIT unchanged

* fix sample rowcount test

* replace max global limit with existing sql max row limit

* fix test

* make max_limit optional in util

* improve comments

tests/integration_tests/query_context_tests.py

@@ -90,6 +90,7 @@ class TestQueryContext(SupersetTestCase):
                 self.assertEqual(post_proc["operation"], payload_post_proc["operation"])
                 self.assertEqual(post_proc["options"], payload_post_proc["options"])
 
+    @pytest.mark.usefixtures("load_birth_names_dashboard_with_slices")
     def test_cache(self):
         table_name = "birth_names"
         table = self.get_table(name=table_name)