Evictable constructor Null safety

1. sendbird_sdk
2. policy
3. Evictable
4. Evictable constructor

Evictable class

1. Constructors
2. Evictable
3. Properties
4. hashCode
5. policy
6. runtimeType
7. Methods
8. evict
9. noSuchMethod
10. toString
11. Operators
12. operator ==