Implement performance optimizations for the continuous particle mode of the "Spin" screen

[AgustinVallejo]

Similar to #62

I'm also doing the profiler check for the Spin screen, and on my machine I get pretty good results (60fps at max particles)... @Nancy-Salpepi could you also run the experiment on iPad and Chromebook?

https://phet-dev.colorado.edu/html/quantum-measurement/1.0.0-dev.8/phet/quantum-measurement_all_phet.html?profiler

I believe this would be at maximum optimization since it already used a canvas for rendering, but doesn't hurt to try.

[Nancy-Salpepi]

Looking great on the iPad 9th generation and the Lenovo 2e Chromebook at 60 FPS!!