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/modules/reagents/reagent_containers/dropper.dm

@@ -7,6 +7,7 @@
 	desc = "A dropper. Transfers 5 units."
 	icon_state = "dropper"
 	item_state = "dropper"
+	belt_icon = "dropper"
 	amount_per_transfer_from_this = 5
 	possible_transfer_amounts = list(1, 2, 3, 4, 5)
 	volume = 5

code/modules/reagents/reagent_containers/glass_containers.dm

@@ -119,6 +119,7 @@
 	icon = 'icons/obj/chemical.dmi'
 	icon_state = "beaker"
 	item_state = "beaker"
+	belt_icon = "beaker"
 	materials = list(MAT_GLASS=500)
 	var/obj/item/assembly_holder/assembly = null
 	var/can_assembly = 1
@@ -226,6 +227,7 @@
 	name = "vial"
 	desc = "A small glass vial. Can hold up to 25 units."
 	icon_state = "vial"
+	belt_icon = "vial"
 	materials = list(MAT_GLASS=250)
 	volume = 25
 	amount_per_transfer_from_this = 10

code/modules/reagents/reagent_containers/hypospray.dm

@@ -8,6 +8,7 @@
 	icon = 'icons/obj/hypo.dmi'
 	item_state = "hypo"
 	icon_state = "hypo"
+	belt_icon = "hypospray"
 	amount_per_transfer_from_this = 5
 	volume = 30
 	possible_transfer_amounts = list(1,2,3,4,5,10,15,20,25,30)
@@ -101,6 +102,7 @@
 	desc = "A rapid and safe way to stabilize patients in critical condition for personnel without advanced medical knowledge."
 	icon_state = "autoinjector"
 	item_state = "autoinjector"
+	belt_icon = "autoinjector"
 	amount_per_transfer_from_this = 10
 	possible_transfer_amounts = list(10)
 	volume = 10

code/modules/reagents/reagent_containers/spray.dm

@@ -4,6 +4,7 @@
 	icon = 'icons/obj/janitor.dmi'
 	icon_state = "cleaner"
 	item_state = "cleaner"
+	belt_icon = "space_cleaner"
 	flags = NOBLUDGEON
 	container_type = OPENCONTAINER
 	slot_flags = SLOT_BELT
@@ -150,6 +151,7 @@
 	icon = 'icons/obj/items.dmi'
 	icon_state = "pepperspray"
 	item_state = "pepperspray"
+	belt_icon = null
 	volume = 40
 	spray_maxrange = 4
 	amount_per_transfer_from_this = 5
@@ -162,6 +164,7 @@
 	icon = 'icons/obj/hydroponics/harvest.dmi'
 	icon_state = "sunflower"
 	item_state = "sunflower"
+	belt_icon = null
 	amount_per_transfer_from_this = 1
 	volume = 10
 	list_reagents = list("water" = 10)
@@ -235,5 +238,6 @@
 	icon = 'icons/obj/hydroponics/equipment.dmi'
 	icon_state = "plantbgone"
 	item_state = "plantbgone"
+	belt_icon = null
 	volume = 100
 	list_reagents = list("glyphosate" = 100)

code/modules/reagents/reagent_containers/syringes.dm

@@ -8,6 +8,7 @@
 	icon = 'icons/goonstation/objects/syringe.dmi'
 	item_state = "syringe_0"
 	icon_state = "0"
+	belt_icon = "syringe"
 	amount_per_transfer_from_this = 5
 	possible_transfer_amounts = list()
 	volume = 15