Issue #2254495 by sun, ParisLiakos, alexpott: Followup to Move language_admin_predefined_list to ConfigurableLanguageManager.
Issue #2209337 by tstoeckler: Remove hidden property from test extensions.
Issue #2198713 by tstoeckler: Add a settings.php variable to allow to discover/enable test extensions at regular runtime.
Issue #2266547 by alexpott, sun: TestKernel is not adding its service provider correctly.