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/timer.dm

@@ -16,9 +16,7 @@
   * lists. The object at a given index in bucket_list is a /datum/timedevent, the head of a circular list, which has prev
   * and next references for the respective elements in that bucket's circular list.
   */
-var/datum/controller/subsystem/timer/SStimer
-
-/datum/controller/subsystem/timer
+SUBSYSTEM_DEF(timer)
 	name = "Timer"
 	wait = 1 //SS_TICKER subsystem, so wait is in ticks
 	priority = SS_PRIORITY_TIMER
@@ -55,8 +53,7 @@ var/datum/controller/subsystem/timer/SStimer
 	/// How many times bucket was reset
 	var/bucket_reset_count = 0
 
-/datum/controller/subsystem/timer/New()
-	NEW_SS_GLOBAL(SStimer)
+/datum/controller/subsystem/timer/PreInit()
 	bucket_list.len = BUCKET_LEN
 	head_offset = world.time
 	bucket_resolution = world.tick_lag