AnimationState/AnimationTest Changes

In GeckoLib4, users would take an instance of AnimationState in their controller predicates, using it to handle the animation stages and PlayState. This caused issues with users confusing the class with the vanilla AnimationState class, and it also posed a problem when introducing the RenderState object.

To rectify these issues, the AnimationController predicate will now provide an instance of AnimationTest. It works mostly the same way, but splitting it into its own object meant I could hide away the parts that aren't relevant to you at the time of the predicate, eliminate some naming confusion.