Forecon SMG ammo is moved to their belt (#7433)

# About the pull request
Forecon now gets a rig filled with their m39 and mags, instead of having
just the m39 rig itself. This touches on both the survivor and
adminspawn ERT variants.

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# Explain why it's good for the game

being forced to toss away all your sidearm mags just so that you can
have space to hold stuff kinda sucks, especially when every other
sidearm spawn that forecon has keeps its' mags in the belt

# Testing Photographs and Procedure
Inventory before, note how there's no storage unless you toss out mags
(or move your radio)


![image](https://github.com/user-attachments/assets/23c57f3b-6863-4ecb-b265-1a48be299fb8)

Inventory after:


![image](https://github.com/user-attachments/assets/f4866b94-2cdb-43dc-a62f-881f8d0fef39)

# Changelog
:cl:
balance: Forecon M39 spawn now has its spawn ammo in belt, instead of in
satchel.
/:cl:

code/game/objects/items/storage/belt.dm

@@ -1318,6 +1318,16 @@
 			"icon_x" = -11,
 			"icon_y" = -5))
 
+/obj/item/storage/belt/gun/m39/full/fill_preset_inventory()
+	handle_item_insertion(new /obj/item/weapon/gun/smg/m39(src))
+	for(var/i = 1 to storage_slots - 1)
+		new /obj/item/ammo_magazine/smg/m39(src)
+
+/obj/item/storage/belt/gun/m39/full/extended/fill_preset_inventory()
+	handle_item_insertion(new /obj/item/weapon/gun/smg/m39(src))
+	for(var/i = 1 to storage_slots - 1)
+		new /obj/item/ammo_magazine/smg/m39/extended(src)
+
 #define MAXIMUM_MAGAZINE_COUNT 2
 
 /obj/item/storage/belt/gun/xm51

code/modules/gear_presets/survivors/lv_522/forcon_survivors.dm

@@ -72,10 +72,7 @@
 			new_human.equip_to_slot_or_del(new /obj/item/ammo_magazine/pistol/m1911(new_human), WEAR_IN_BELT)
 			new_human.equip_to_slot_or_del(new /obj/item/ammo_magazine/pistol/m1911(new_human), WEAR_IN_BELT)
 		if(3 , 4)
-			new_human.equip_to_slot_or_del(new /obj/item/storage/large_holster/m39, WEAR_WAIST)
-			new_human.equip_to_slot_or_del(new /obj/item/weapon/gun/smg/m39(new_human), WEAR_IN_BELT)
-			new_human.equip_to_slot_or_del(new /obj/item/ammo_magazine/smg/m39/extended(new_human), WEAR_IN_BACK)
-			new_human.equip_to_slot_or_del(new /obj/item/ammo_magazine/smg/m39/extended(new_human), WEAR_IN_BACK)
+			new_human.equip_to_slot_or_del(new /obj/item/storage/belt/gun/m39/full/extended, WEAR_WAIST)
 		if(5)
 			new_human.equip_to_slot_or_del(new /obj/item/device/motiondetector(new_human),WEAR_WAIST)
 

code/modules/gear_presets/uscm_forecon.dm

@@ -73,10 +73,7 @@
 			new_human.equip_to_slot_or_del(new /obj/item/ammo_magazine/pistol/m1911(new_human), WEAR_IN_BELT)
 			new_human.equip_to_slot_or_del(new /obj/item/ammo_magazine/pistol/m1911(new_human), WEAR_IN_BELT)
 		if(3 , 4)
-			new_human.equip_to_slot_or_del(new /obj/item/storage/belt/gun/m39, WEAR_WAIST)
-			new_human.equip_to_slot_or_del(new /obj/item/weapon/gun/smg/m39(new_human), WEAR_IN_BELT)
-			new_human.equip_to_slot_or_del(new /obj/item/ammo_magazine/smg/m39/extended(new_human), WEAR_IN_BELT)
-			new_human.equip_to_slot_or_del(new /obj/item/ammo_magazine/smg/m39/extended(new_human), WEAR_IN_BELT)
+			new_human.equip_to_slot_or_del(new /obj/item/storage/belt/gun/m39/full/extended, WEAR_WAIST)
 		if(5)
 			new_human.equip_to_slot_or_del(new /obj/item/device/motiondetector(new_human),WEAR_WAIST)