NERtcVideoDeviceState constructor Null safety

1. netease_roomkit
2. netease_roomkit
3. NERtcVideoDeviceState
4. NERtcVideoDeviceState constructor

NERtcVideoDeviceState class

1. Constructors
2. NERtcVideoDeviceState
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. toString
9. Operators
10. operator ==
11. Constants
12. closed
13. disconnected
14. freezed
15. initialized
16. opened
17. unInitialized
18. unknownError