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)

3650 Update plugin_platform_interface min version (cla: yes, p: battery, p: camera, p: connectivity, p: device_info, p: file_selector, p: google_maps_flutter, p: image_picker, p: path_provider, p: url_launcher, p: wifi_info_flutter)

3663 [image_picker] Run CocoaPods iOS tests in RunnerUITests target (cla: yes, p: image_picker, platform-ios)

3676 [image_picker] fix flutter/flutter#71927 (cla: yes, p: image_picker, platform-ios, waiting for tree to go green)