Improves belt item overlay code, Adds new belt item overlay sprites (#17568)

* belt-improvements-and-sprites

* fixes my fix of botany belt allowed contents

code/game/objects/items/stacks/medical.dm

@@ -171,6 +171,7 @@
 	singular_name = "advanced trauma kit"
 	desc = "An advanced trauma kit for severe injuries."
 	icon_state = "traumakit"
+	belt_icon = "traumakit"
 	max_amount = 6
 	heal_brute = 25
 	stop_bleeding = 0
@@ -219,6 +220,7 @@
 	singular_name = "advanced burn kit"
 	desc = "An advanced treatment kit for severe burns."
 	icon_state = "burnkit"
+	belt_icon = "burnkit"
 	heal_burn = 25
 
 /obj/item/stack/medical/ointment/advanced/cyborg