Chemical splash fixes, distillery fix, and syringe gun fix. (#19219)

* Fixes distillery always using atmos air

Distillery did not have a return_air() proc, so it would default to the atmos air even when piped. This fixes that.

* Fixes syringe guns allowing loading of multiple syringes

* Affect_touch changes

* Some more changes

* Reworks cyanide

code/modules/projectiles/guns/launcher/syringe_gun.dm

@@ -19,6 +19,9 @@
 
 /obj/item/syringe_cartridge/attackby(obj/item/I, mob/user)
 	if(istype(I, /obj/item/reagent_containers/syringe))
+		if(syringe)
+			to_chat(user, span_warning("[src] already has a syringe loaded!"))
+			return
 		syringe = I
 		to_chat(user, span_notice("You carefully insert [syringe] into [src]."))
 		user.remove_from_mob(syringe)