3363 [cross_file] Make sure saveTo returns a Future (cla: yes)

3364 [camera_platform_interface] Added imageFormatGroup to initialize (cla: yes)

3365 [camera] Added maxVideoDuration to startVideoRecording (cla: yes)

3366 [battery] Migrate battery_plugin_interface to null safety (cla: yes)

3367 [camera] Fix flash/torch not working on some Android devices. (cla: yes)

3369 [camera_platform_interface] Add platform interface methods for setting auto focus. (cla: yes)

3370 [camera] Add iOS and Android implementations for managing auto focus. (cla: yes)

3375 [camera] Fix video recording exception on Android (cla: yes)