Update the animators object in the animator cells on refresh

[Nicolás Uriel Navall]

Describe the issue

When refreshing the animator's list in the Animator Panel we don't refresh cells from entities that are already there. Unfortunately, this means that if these entities had their list of animation list updated inside the game, then we wouldn't update them in the dropdown.

So we should update the Unity animator object inside the wrapper and the dropdown, or just delete all cells in the list.

[Nicolás Uriel Navall]

Solved in 171ee3f by instead appending new animations to the existing ones. That way we let the user have an even bigger list of animations to choose from if they update it at the right moment.

Maybe we can mock the property in the future to automatically detect when new animations are added so we can add them to our existing list of animation clips.