NERtcAudioDevice constructor Null safety

1. nertc
2. nertc
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