2750 Use Xvfb for Linux desktop tests (cla: yes)

2751 [Many]Update lower dart bound to 2.1.0 (cla: yes)

2752 [google_maps_flutter] add todo on skipped test. (cla: yes)

2755 [image_picker] fixes for iOS which doesn’t present camera/albums with more complex navigation (cla: yes, in review)

2757 [url_launcher] Initialize previousAutomaticSystemUiAdjustment in launch (bugfix, cla: yes)

2759 [video_player] fixed detach from engine logic (cla: yes)

2761 [image_picker] updated VALID_ARCHS to support iPhone simulator (cla: yes)

2763 [webview_flutter] Add support for passing a failing url (cla: yes)