NERtcDegradationPreference constructor Null safety

1. netease_roomkit
2. netease_roomkit
3. NERtcDegradationPreference
4. NERtcDegradationPreference constructor

NERtcDegradationPreference class

1. Constructors
2. NERtcDegradationPreference
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. toString
9. Operators
10. operator ==
11. Constants
12. degradationBalanced
13. degradationDefault
14. degradationMaintainFrameRate
15. degradationMaintainQuality