Updates subsystem definitions to new standards. (#17470)

* My heart is dragging me down into...

...oblivion!

* drifting closer to the edge but she won't have me

* ever round me we are dead before we meet her

* for the last time

* wake up in sweat

* n

* fff

* uff

---------

Co-authored-by: Matt Atlas <liermattia@gmail.com>

code/controllers/subsystems/orbit.dm

@@ -1,6 +1,4 @@
-var/datum/controller/subsystem/orbit/SSorbit
-
-/datum/controller/subsystem/orbit
+SUBSYSTEM_DEF(orbit)
 	name = "Orbits"
 	priority = SS_PRIORITY_ORBIT
 	wait = 2
@@ -10,9 +8,6 @@ var/datum/controller/subsystem/orbit/SSorbit
 	var/list/currentrun = list()
 	var/list/processing = list()
 
-/datum/controller/subsystem/orbit/New()
-	NEW_SS_GLOBAL(SSorbit)
-
 /datum/controller/subsystem/orbit/Recover()
 	src.processing = SSorbit.processing