Changes AMMO_BOX_FULL_EMPTY to be either -full or -empty on a magazine, rather than the old behavior of using the max ammo of the magazine (#73736)

## About The Pull Request

As the title might imply:

AMMO_BOX_FULL_EMPTY will now look for sprites with -full and -empty,
rather than -[whatever the max ammo was] and -0
## Why It's Good For The Game

If a magazine is only going to have two states, that being having ammo
and not having ammo, why do I have to fuck with finding the capacity of
the magazine? On the other hand, why should anyone trying to change the
ammo count of a magazine have to fuck with the sprite naming for what
should otherwise just be a change of a var.
## Changelog
🆑
code: AMMO_BOX_FULL_EMPTY now looks for -full and -empty for sprites,
rather than -[max ammo of that magazine] and -0
/🆑

code/modules/projectiles/boxes_magazines/external/pistol.dm

@@ -1,7 +1,7 @@
 /obj/item/ammo_box/magazine/m10mm
 	name = "pistol magazine (10mm)"
 	desc = "A gun magazine."
-	icon_state = "9x19p-8"
+	icon_state = "9x19p-full"
 	base_icon_state = "9x19p"
 	ammo_type = /obj/item/ammo_casing/c10mm
 	caliber = CALIBER_10MM
@@ -42,7 +42,7 @@
 
 /obj/item/ammo_box/magazine/m9mm
 	name = "pistol magazine (9mm)"
-	icon_state = "9x19p-8"
+	icon_state = "9x19p-full"
 	base_icon_state = "9x19p"
 	ammo_type = /obj/item/ammo_casing/c9mm
 	caliber = CALIBER_9MM

code/modules/projectiles/boxes_magazines/external/rifle.dm

@@ -1,7 +1,7 @@
 /obj/item/ammo_box/magazine/m10mm/rifle
 	name = "rifle magazine (10mm)"
 	desc = "A well-worn magazine fitted for the surplus rifle."
-	icon_state = "75-8"
+	icon_state = "75-full"
 	base_icon_state = "75"
 	ammo_type = /obj/item/ammo_casing/c10mm
 	max_ammo = 10