cesium particle system frame rate drops sharply after losing focus and returning

[engineerhe]

Hi,cesium teams,
I found a bug.When you lose focus and come back, the more particles you emit per unit of time, the more you drop the frame.

[ggetz]

Thanks for the report @engineerhe! I believe this is already being tracked in #9266. I'm going to close this issue to keep the discussion in the original issue. Thanks!