[2D][Animation] Sprite Resolver component not updated when new categories/labels are added into Sprite Library asset (e.g. added a new category).

Repro steps:
1. Created a Sprite Library Asset and added a new category called "head" and populated with different variations.
2. Added a Sprite Library and Sprite Resolver component to my GameObject.
3. Opened up my Sprite Library Asset again. This time to add more categories e.g. "body" and again populated with different variations.
4. Went back to my GameObject and realised that my Sprite Resolver component didn't refresh. The dropdown only still showed "head" and I was expecting to see the newly added category "body" too.
5. Had to remove both the Sprite Library and Sprite Resolver component and re-added them to my GameObject in order to see my new categories with "head" and "body".

Expected result: Sprite Resolver component didn't refresh after updating Sprite Library asset
Actual result: Sprite Resolver component refreshes after updating Sprite Library asset