[ticket/11880] Move get_schema_steps function to a migrator helper class

PHPBB3-11880

tests/test_framework/phpbb_functional_test_case.php

@@ -194,7 +194,8 @@ class phpbb_functional_test_case extends phpbb_test_case
 			$phpbb_root_path,
 			$php_ext,
 			self::$config['table_prefix'],
-			array()
+			array(),
+			new \phpbb\db\migration\helper()
 		);
 		$container = new phpbb_mock_container_builder();
 		$container->set('migrator', $migrator);