Return standardized return values from Animation new, render and interact instead of tuples.

[doughsay]

new and interact both return {render_in, state} and render returns {render_in, colors, state}. They are so close to being the same, let's see if we can come up with a good refactor here that makes these all a shared struct definition instead of "almost the same" tuples.

[doughsay]

We discussed that new should not return render_in, as all animations we can think of will always return 0.