Refactored movement observable away (#20083)

Refactored movement observable away, use only the signal.
Some tweaks to the signal.

code/controllers/subsystems/orbit.dm

@@ -1,46 +0,0 @@
-SUBSYSTEM_DEF(orbit)
-	name = "Orbits"
-	priority = SS_PRIORITY_ORBIT
-	wait = 2
-	flags = SS_NO_INIT|SS_TICKER
-	runlevels = RUNLEVELS_PLAYING
-
-	var/list/currentrun = list()
-	var/list/processing = list()
-
-/datum/controller/subsystem/orbit/Recover()
-	src.processing = SSorbit.processing
-
-/datum/controller/subsystem/orbit/stat_entry(msg)
-	msg = "P:[processing.len]"
-	return ..()
-
-/datum/controller/subsystem/orbit/fire(resumed = 0)
-	if (!resumed)
-		src.currentrun = processing.Copy()
-
-	//cache for sanic speed (lists are references anyways)
-	var/list/currentrun = src.currentrun
-
-	while (currentrun.len)
-		var/datum/orbit/O = currentrun[currentrun.len]
-		currentrun.len--
-		if (!O)
-			processing -= O
-			if (MC_TICK_CHECK)
-				return
-			continue
-		if (!O.orbiter)
-			qdel(O)
-			if (MC_TICK_CHECK)
-				return
-			continue
-		if (O.lastprocess >= world.time) //we already checked recently
-			if (MC_TICK_CHECK)
-				return
-			continue
-		var/targetloc = get_turf(O.orbiting)
-		if (targetloc != O.lastloc || O.orbiter.loc != targetloc)
-			O.Check(targetloc)
-		if (MC_TICK_CHECK)
-			return