NERtcSubStreamContentPrefer constructor Null safety

1. netease_roomkit
2. netease_roomkit
3. NERtcSubStreamContentPrefer
4. NERtcSubStreamContentPrefer constructor

NERtcSubStreamContentPrefer class

1. Constructors
2. NERtcSubStreamContentPrefer
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. toString
9. Operators
10. operator ==
11. Constants
12. details
13. motion