2744 [video_player]: added test class to fix video_player unit tests (cla: yes)

2745 [video_player]: fixed platform_interface unit tests (cla: yes)

2746 [google_maps_flutter] use WaitUntilTouchesEndedPolicy to fix the cameraIdle not called issue on iOS (cla: yes)

2747 [android_alarm_manager] update dart deps lower bound to 2.1.0 (cla: yes)

2748 [battery] update dart deps lower bound to 2.1.0 (cla: yes)

2749 [camera] Update lower bound of dart dependency to 2.1.0. (cla: yes)

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