3932 Move integration test to null safety for multiple plugins (cla: yes, p: webview_flutter, p: image_picker, p: in_app_purchase, p: wifi_info_flutter, p: quick_actions, p: connectivity, p: device_info, platform-ios, platform-android, platform-macos)

3958 [webview_flutter] Fix race in test (cla: yes, p: webview_flutter)

3960 Use collection and box literals in ObjC code (cla: yes, p: webview_flutter, p: camera, p: google_maps_flutter, p: image_picker, p: in_app_purchase, platform-ios)

3995 [webview_flutter] Add iOS integration tests (cla: yes, waiting for tree to go green, p: webview_flutter, platform-ios)