3461 [ci][image_picker][webviews_flutter] enable Xcode 12  (cla: yes, p: image_picker, p: webview_flutter, waiting for tree to go green)

3481 [shared_preferences] Removed deprecated AsyncTask API (cla: yes, p: shared_preferences, platform-android, waiting for tree to go green)

3484 Remove amirh from CODEOWNERS (cla: yes, waiting for tree to go green)

3492 [image_picker_platform_interface] migrate to nnbd  (cla: yes, nnbd, p: image_picker, waiting for tree to go green)

3493 Add plugin issue query to README (cla: yes, waiting for tree to go green)