Renderer-based particle system

[leilei-]

I haven't been working on this in a while. There's still some glitches though

• Different particle sets incomplete. They were to mimic UT, Half-Life, Q2, etc.
• Particles flicker into visibility right when they die (most noticable with smoke). I've had this bug in Engoo before and fixed it there years ago
• Trailing particles not yet reimplemented
• Some particle effects start late or don't start at all.
• Particle physics are processed per portal, so mirrors/portals will make the particles calculate their tracechecks even more with some performance loss
• Particles don't get excluded in the pvs i don't think. there can be situations of overdraw
• by accident I committed a new icon too. purely cosmetic and reflects some of the new oa3 ui aesthetic