CTF machines are only added to processing when CTF starts (#3360)

<!-- Write **BELOW** The Headers and **ABOVE** The comments else it may
not be viewable. -->
<!-- You can view Contributing.MD for a detailed description of the pull
request process. -->

## About The Pull Request
small optimization to reduce the size of SSmachines processing
<!-- Describe The Pull Request. Please be sure every change is
documented or this can delay review and even discourage maintainers from
merging your PR! -->

## Why It's Good For The Game

<!-- Please add a short description of why you think these changes would
benefit the game. If you can't justify it in words, it might not be
worth adding. -->

## Changelog

:cl:
code: ctf machines now only process while ctf is running
/:cl:

<!-- Both :cl:'s are required for the changelog to work! You can put
your name to the right of the first :cl: if you want to overwrite your
GitHub username as author ingame. -->
<!-- You can use multiple of the same prefix (they're only used for the
icon ingame) and delete the unneeded ones. Despite some of the tags,
changelogs should generally represent how a player might be affected by
the changes rather than a summary of the PR's contents. -->

_maps/map_files/generic/CentCom.dmm

@@ -154,7 +154,7 @@
 /turf/open/floor/plating,
 /area/ctf)
 "agI" = (
-/obj/machinery/power/emitter/energycannon{
+/obj/machinery/power/emitter/energycannon/ctf{
 	active = 0
 	},
 /turf/open/floor/plating,
@@ -163,7 +163,7 @@
 /turf/open/floor/plating,
 /area/ctf)
 "aha" = (
-/obj/machinery/power/emitter/energycannon{
+/obj/machinery/power/emitter/energycannon/ctf{
 	active = 0;
 	dir = 1
 	},

code/modules/awaymissions/capture_the_flag.dm

@@ -171,6 +171,7 @@
 	icon = 'icons/obj/device.dmi'
 	icon_state = "syndbeacon"
 	resistance_flags = INDESTRUCTIBLE
+	processing_flags = START_PROCESSING_MANUALLY
 	var/team = WHITE_TEAM
 	var/team_span = ""
 	//Capture the Flag scoring
@@ -347,6 +348,7 @@
 
 /obj/machinery/capture_the_flag/proc/start_ctf()
 	ctf_enabled = TRUE
+	START_PROCESSING(SSmachines, src)
 	for(var/d in dead_barricades)
 		var/obj/effect/ctf/dead_barricade/D = d
 		D.respawn()
@@ -378,6 +380,7 @@
 
 /obj/machinery/capture_the_flag/proc/stop_ctf()
 	ctf_enabled = FALSE
+	STOP_PROCESSING(SSmachines, src)
 	arena_reset = FALSE
 	var/area/A = get_area(src)
 	for(var/i in GLOB.mob_list)

code/modules/awaymissions/mission_code/challenge.dm

@@ -35,3 +35,13 @@
 
 /obj/machinery/power/emitter/energycannon/RefreshParts()
 	return
+
+/obj/machinery/power/emitter/energycannon/ctf
+	processing_flags = START_PROCESSING_MANUALLY
+
+/obj/machinery/power/emitter/energycannon/ctf/proc/toggle_ctf(ctf_enabled)
+	src.active = ctf_enabled
+	if(ctf_enabled)
+		START_PROCESSING(SSmachines, src)
+	else
+		STOP_PROCESSING(SSmachines, src)

code/modules/power/singularity/emitter.dm

@@ -357,16 +357,6 @@
 	if(user)
 		user.visible_message("<span class='warning'>[user.name] emags [src].</span>", "<span class='notice'>You short out the lock.</span>")
 
-/obj/machinery/power/emitter/ctf
-	name = "Energy Cannon"
-	active = TRUE
-	active_power_usage = FALSE
-	idle_power_usage = FALSE
-	locked = TRUE
-	req_access_txt = "100"
-	welded = TRUE
-	use_power = FALSE
-
 /obj/machinery/power/emitter/welded/Initialize()
 	welded = TRUE
 	return ..()