NERtcCameraCapturePreference constructor Null safety

1. nertc
2. nertc
3. NERtcCameraCapturePreference
4. NERtcCameraCapturePreference constructor

NERtcCameraCapturePreference class

1. Constructors
2. NERtcCameraCapturePreference
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. toString
9. Operators
10. operator ==
11. Constants
12. kDefault
13. kManual
14. kQuality