NERtcAudioDevice constructor Null safety

1. yunxin_roomkit
2. roomkit
3. NERtcAudioDevice
4. NERtcAudioDevice constructor

NERtcAudioDevice class

1. Constructors
2. NERtcAudioDevice
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. toString
9. Operators
10. operator ==
11. Constants
12. bluetoothHeadset
13. earpiece
14. speakerPhone
15. wiredHeadset