OW/QC style player outlines

[nickalreadyinuse]

Implements Quake Champions/Overwatch style player outlines in-game (server permission gated) and for spectators (always permitted).

[is-this-c]

Impressive. Any ideas wrt aliasing? outline_thickness at 2.0 is nice. But I notice sometimes X-rays do not draw below a player label e.g. upon join. If however you move close enough it starts to render properly wherever. It also sometimes does not render outside or inside water relative to camera.

[nickalreadyinuse]

There's probably an approach that makes more sense than a fixed-thickness outline. I tried rendering 3 lines of different thickness/opacity and blending them to make the outlines less sharp and debuggy looking, but decided against it because at farther ranges the silhouette of the character was not as clear to me and it just looked a bit sloppy in some way. Also trying to strike some (maybe impossible) balance because they really boost visibility at long range quite a bit more than even fullbrights IMO.

I'll check on the player label issue, not something I noticed. There is also still an issue with this where player animations are freezing sometimes as well (visible for X-rays) which is probably just another thing the engine culls. Water - thanks, didn't even check that. I try to forget water exists in this game.