Replace three `Timer` with postprocessing `Timer`

We recently added the three Timer class by Mugen. After this @vanruesc made us aware that he has a modified version inside of pmndrs/postprocessing that can be found here. I'm thinking we should use the same Timer class as pmndrs/postprocessing so that a shared timer is possible between pmndrs libraries.

Notable differences are using getters instead of get functions, reset properly resets the whole timer, autoReset manages the timer with page visibility without constructor side effects and the rAF timestamp can be passed into update (though this optimization was added to the three Timer recently).

The only downside I see is when the three Timer gets merged its API will likely be different from ours. However, I think if we do extend what looks like a better Timer design it can influence the final API and allow us to experiment with new ideas.

Start with the referenced pmndrs/postprocessing src/utils/Timer.ts and compare it with the three Timer implementations and their call sites. Confirm the API differences and replace the existing timers with the postprocessing design, updating uses as needed so a shared timer is possible without breaking behavior.