3621 [quick_action] fix delegate methods not called on iOS (cla: yes, p: quick_actions, platform-ios, waiting for tree to go green)

3646 move integration test to null safety for multiple plugins. (cla: yes, nnbd, p: connectivity, p: device_info, p: image_picker, p: in_app_purchase, p: quick_actions, p: webview_flutter, p: wifi_info_flutter)