[Rewrite] Native Animation Support For Generators

As discussed in the Discord today, I had an idea for animating generators in a semi-sane way with decently broad-range support. Essentially, a "supported" generator model would have four animations with the following names:

1. generator_activate
2. generator_deactivate
3. generator_runloop
4. generator_idle

These four states should handle all states (minus Malfunctioning) of a generator, and should be unique enough to not have an "unsupported" model suddenly trigger an odd animation. The sc_generator entity's clientside think should then check if its set model has the above animation for the state it's in/transitioning to and enable it.

This should allow for any "supported" model to animate semi-dynamically when set, allowing for creative (read: silly) uses of generators for other uses. Yes, this means that a player can have a very tall spinning Windmill that somehow produces Methane and, you know what? I'm fine with that.