Improve particle system memory management performance

[pjcozzi]

From #5212 (comment)

In the fireworks Sandcastle example, I would not expect this to be 10% of the profile?

and #5212 (comment)

The problem is the memory management again. Sometimes more particles are created than was estimated and they get removed later. This causes the number of commands from the billboard collection to change. For every new command, it generates the OIT shader and looks it up in the cache.

[hpinkos]

The Particle System Fireworks sandcastle demo won't load in Firefox for me, it says the web page is slowing down the browser. Is this why?

[pjcozzi]

@hpinkos most likely not. It loads OK for me on Mac Firefox 54. Can you confirm this doesn't load for you with a clean build and clear cache in Firefox 54, check out the console, and then submit a new issue if it is a problem?

[hpinkos]

Okay, it worked after I cleared my cache