ExposeOnSpawn pins no longer read default values from the linked class

This is technically a regression that was introduced in 5.5. This was intentionally changed in order to address a separate issue [Link Removed]. Additionally, this makes it explicit that the exposed pins always override the defaults on the spawned object.

However, there have been use cases for the previous behavior. Since we can't infer what the user wants, we'll need to additional support for specifying if a exposed pins should use the class's default value or not.

1. Create a bp class BP_Parent with some properties with a default value.
2. Create a child class BP_Child that derives from BP_Parent
3. Set different default values on BP_Child for the properties inherited from BP_Parent
4. Create another class BP_ActorSpawner, add a property of class type BP_Parent
5. Set the class properties value to BP_Child
6. Pass the class property into SpawnActor

Expected: BP_Childs overriden defaults are used.
Actual Result: BP_Childs defaults are ignored and instead BP_Parents are used.