Save 0.6-0.7s of init time by splitting registering lists of signals into its own proc, and optimizing QDELETED (#71056)

- Makes QDELETED use isnull(x) instead of !x, giving about 0.2 to 0.25s
of speed.
- Make disposal constructs only update icon state rather than go through
expensive overlay code. Unfortunately did not have much effect, but is
something they should've been doing nonetheless.
- Makes RegisterSignal only take signals directly as opposed to
allocating a fresh list of signals. Very few consumers actually used
this and it costs about 0.4s. Also I think this is just a bad API anyway
and that separate procs are important

`\bRegisterSignal\((.*)list\(` replaced with `RegisterSignals($1list(`

code/modules/wiremod/shell/airlock.dm

@@ -156,7 +156,7 @@
 	. = ..()
 	if(istype(shell, /obj/machinery/door/airlock))
 		attached_airlock = shell
-		RegisterSignal(shell, list(
+		RegisterSignals(shell, list(
 			COMSIG_OBJ_ALLOWED,
 			COMSIG_AIRLOCK_SHELL_ALLOWED,
 		), PROC_REF(handle_allowed))

code/modules/wiremod/shell/assembly.dm

@@ -34,7 +34,7 @@
 	signal = add_output_port("Signal", PORT_TYPE_SIGNAL)
 
 /obj/item/circuit_component/assembly_input/register_shell(atom/movable/shell)
-	RegisterSignal(shell, list(COMSIG_ASSEMBLY_PULSED, COMSIG_ITEM_ATTACK_SELF), PROC_REF(on_pulsed))
+	RegisterSignals(shell, list(COMSIG_ASSEMBLY_PULSED, COMSIG_ITEM_ATTACK_SELF), PROC_REF(on_pulsed))
 
 /obj/item/circuit_component/assembly_input/unregister_shell(atom/movable/shell)
 	UnregisterSignal(shell, list(COMSIG_ASSEMBLY_PULSED, COMSIG_ITEM_ATTACK_SELF))

code/modules/wiremod/shell/dispenser.dm

@@ -164,7 +164,7 @@
 			var/obj/item/circuit_component/vendor_component/vendor_component = new(parent)
 			parent.add_component(vendor_component, user)
 			vendor_components += vendor_component
-			RegisterSignal(vendor_component, list(
+			RegisterSignals(vendor_component, list(
 				COMSIG_PARENT_QDELETING,
 				COMSIG_CIRCUIT_COMPONENT_REMOVED,
 			), PROC_REF(remove_vendor_component))