Orbits are now a subsystem (#20632)

* Sleepless perfect orbits #MOGA
We bind to Moved() and use datums and lists to track the orbits, no more sleeps, no more delay.

* Adds some null checks to orbit checks

* Forget to set orbiting.
Also sets orbiters before orbiting, to avoid edge cases of deleting a list then recreating it.

* Improves orbit, adds subsystem for orbits.
Most orbit loc changes will happen on move, subsystem runs every 2 ticks to make up for when that isn't the case.

code/modules/mob/dead/observer/observer.dm

@@ -383,7 +383,7 @@ This is the proc mobs get to turn into a ghost. Forked from ghostize due to comp
 	var/orbitsize = (I.Width()+I.Height())*0.5
 	orbitsize -= (orbitsize/world.icon_size)*(world.icon_size*0.25)
 
-	if(orbiting != target)
+	if(orbiting && orbiting.orbiting != target)
 		src << "<span class='notice'>Now orbiting [target].</span>"
 
 	var/rot_seg
@@ -403,13 +403,14 @@ This is the proc mobs get to turn into a ghost. Forked from ghostize due to comp
 	orbit(target,orbitsize, FALSE, 20, rot_seg)
 
 /mob/dead/observer/orbit()
-	setDir(2 )//reset dir so the right directional sprites show up
+	setDir(2)//reset dir so the right directional sprites show up
+	..()
+
+/mob/dead/observer/stop_orbit()
 	..()
 	//restart our floating animation after orbit is done.
-	sleep 2  //orbit sets up a 2ds animation when it finishes, so we wait for that to end
-	if (!orbiting) //make sure another orbit hasn't started
-		pixel_y = 0
-		animate(src, pixel_y = 2, time = 10, loop = -1)
+	pixel_y = 0
+	animate(src, pixel_y = 2, time = 10, loop = -1)
 
 /mob/dead/observer/verb/jumptomob() //Moves the ghost instead of just changing the ghosts's eye -Nodrak
 	set category = "Ghost"