4191 [camera_platform_interface] Expand camera platform interface to support pausing the camera preview. (cla: yes, waiting for tree to go green, p: camera)

4196 [camera_web] Add takePicture implementation (cla: yes, waiting for tree to go green, p: camera, platform-web)

4197 [camera] Fix camera preview not always rebuilding on orientation change (cla: yes, waiting for tree to go green, p: camera)

4198 Remove pubspec.yaml examples from READMEs (cla: yes, waiting for tree to go green, p: file_selector, p: google_sign_in, p: image_picker, p: in_app_purchase, p: path_provider, p: url_launcher, p: video_player, p: shared_preferences, platform-ios, platform-android, platform-windows, platform-macos, platform-linux, platform-web)