Extends atom_reskin to be more modular/adds support for greyscale reskins in the loadout menu (#94466)

Co-authored-by: SmArtKar <44720187+SmArtKar@users.noreply.github.com>

code/modules/reagents/reagent_containers/medigel.dm

@@ -52,8 +52,7 @@
 	var/self_delay = 30
 	custom_price = PAYCHECK_CREW * 2
 
-/obj/item/reagent_containers/medigel/Initialize(mapload)
-	. = ..()
+/obj/item/reagent_containers/medigel/setup_reskins()
 	if(icon_state == "medigel") // oh yeah baby raw icon state check to make sure we can't reskin preset gels
 		AddComponent(/datum/component/reskinable_item, /datum/atom_skin/med_gel)
 

code/modules/reagents/reagent_containers/spray.dm

@@ -435,8 +435,7 @@
 	righthand_file = 'icons/mob/inhands/equipment/medical_righthand.dmi'
 	volume = 100
 
-/obj/item/reagent_containers/spray/medical/Initialize(mapload, vol)
-	. = ..()
+/obj/item/reagent_containers/spray/medical/setup_reskins()
 	AddComponent(/datum/component/reskinable_item, /datum/atom_skin/med_spray)
 
 /obj/item/reagent_containers/spray/hercuri