3606 Move plugin tool tests over (cla: yes)

3607 [android_intent] Fix Flutter SDK version (cla: yes, nnbd, p: android_intent)

3608 [android_alarm_manager] Bump version for NNBD stable (cla: yes, nnbd, p: android_alarm_manager)

3609 [device_info_platform_interface] handle null value from method channel (cla: yes, nnbd, p: device_info)

3610 [camera_platform_interface] Stable null safety release. (cla: yes, nnbd, p: camera)

3614 [espresso] Update SDK requirement for null-safety (cla: yes, nnbd, p: espresso, waiting for tree to go green)