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

3996 [google_sign_in] Add iOS unit and UI tests (cla: yes, waiting for tree to go green, p: google_sign_in, platform-ios)

3997 [ios_platform_images] Add iOS unit tests (cla: yes, p: ios_platform_images, platform-ios)

3998 [path_provider] Add iOS unit tests (cla: yes, waiting for tree to go green, p: path_provider, platform-ios)

3999 Some small documentation fixes (cla: yes)

4000 [url_launcher] Fix breaking change version conflict (cla: yes, waiting for tree to go green, p: url_launcher)