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/processing/psi.dm

@@ -1,8 +1,6 @@
 var/global/list/psychic_ranks_to_strings = list("Psionically Sensitive", "Psionically Harmonious", "Psionic Apex", "Limitless")
 
-/var/datum/controller/subsystem/processing/psi/SSpsi
-
-/datum/controller/subsystem/processing/psi
+PROCESSING_SUBSYSTEM_DEF(psi)
 	name = "Psionics"
 	priority = SS_PRIORITY_PSYCHICS
 	flags = SS_BACKGROUND
@@ -16,9 +14,6 @@ var/global/list/psychic_ranks_to_strings = list("Psionically Sensitive", "Psioni
 	var/list/all_aura_images = list()
 	var/list/all_psi_complexes = list()
 
-/datum/controller/subsystem/processing/psi/New()
-	NEW_SS_GLOBAL(SSpsi)
-
 /datum/controller/subsystem/processing/psi/fire(resumed)
 	..()
 	if((world.time >= (last_nlom_awareness_check + 30 MINUTES)) && !checking_nlom && !completing_nlom)