Fixes waterpacks and friends not GCing (#19269)

Move nozzles to Initialize
Makes reagents not hold a reference to their atom when they get destroyed

code/modules/reagents/chemistry/holder.dm

@@ -864,3 +864,4 @@
 	addiction_list = null
 	if(my_atom && my_atom.reagents == src)
 		my_atom.reagents = null
+	my_atom = null

code/modules/reagents/reagent_containers.dm

@@ -45,7 +45,8 @@
 
 /obj/item/reagent_containers/Initialize(mapload)
 	. = ..()
-	create_reagents(volume, temperature_min, temperature_max)
+	if(!reagents) // Some subtypes create their own reagents
+		create_reagents(volume, temperature_min, temperature_max)
 	if(!possible_transfer_amounts)
 		verbs -= /obj/item/reagent_containers/verb/set_APTFT
 	if(spawned_disease)