moves abstract_type up to datum, spawners wont spawn them (#92909)

## About The Pull Request
moves all implementations (im aware of) for "Im a parent type dont spawn
me please" to the datum layer to standardized behavior
adds a standerized proc for filtering out "bad" items that we dont want
spawning. applies to it the subtype vendor, gifts, and a new spawner and
mystery box for a random gun (neither playerfacing)
"port" of https://github.com/shiptest-ss13/Shiptest/pull/4621



https://github.com/user-attachments/assets/22f6f0b2-b44e-411a-b3dc-6b97dc0287aa

small warning: I dont have EVERY abstract type defined right now but,
ive done a good enough job for now. Im tired of data entry rn
## Why It's Good For The Game
standardizing behavior. Might be a micro hit to performance however

having this lets us not rely on icon state to determine whether
something is a parent type and makes it much easier to tell something is
a parent type (could be applied further to things like admin spawning
menus and things like that).

need feedback on if this is actually good for the game.
## Changelog
🆑
add: Soda cans show up in the silver slime drink table.
add: Examine tag for items that are not mean to show up ingame.
refactor: Standardizes how gifts rule out abstract types.
fix: gifts no longer check if something has an inhand, massively
expanding the list of potential items.
/🆑

code/modules/projectiles/boxes_magazines/_box_magazine.dm

@@ -3,6 +3,7 @@
 	name = "ammo box (null_reference_exception)"
 	desc = "A box of ammo."
 	icon = 'icons/obj/weapons/guns/ammo.dmi'
+	abstract_type = /obj/item/ammo_box
 	obj_flags = CONDUCTS_ELECTRICITY
 	slot_flags = ITEM_SLOT_BELT
 	inhand_icon_state = "syringe_kit"
@@ -258,6 +259,7 @@
 /obj/item/ammo_box/magazine
 	name = "A magazine (what?)"
 	desc = "A magazine of rounds, they look like error signs... this should probably be reported somewhere."
+	abstract_type = /obj/item/ammo_box/magazine
 	ammo_box_multiload = AMMO_BOX_MULTILOAD_IN // so you can't use a magazine like a bootleg speedloader
 	drop_sound = 'sound/items/handling/gun/ballistics/magazine/magazine_drop1.ogg'
 	pickup_sound = 'sound/items/handling/gun/ballistics/magazine/magazine_pickup1.ogg'

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

@@ -1,6 +1,7 @@
 /obj/item/ammo_box/magazine/toy
 	name = "foam force META magazine"
 	desc = "A magazine specifically designed for foam force \"firearms\". Probably not great for actually killing your fellow spaceman."
+	abstract_type = /obj/item/ammo_box/magazine/toy
 	ammo_type = /obj/item/ammo_casing/foam_dart
 	caliber = CALIBER_FOAM
 

code/modules/projectiles/boxes_magazines/internal/_internal.dm

@@ -1,5 +1,7 @@
 /obj/item/ammo_box/magazine/internal
 	desc = "Oh god, this shouldn't be here"
+	abstract_type = /obj/item/ammo_box/magazine/internal
+	spawn_blacklisted = TRUE
 	obj_flags = CONDUCTS_ELECTRICITY
 	item_flags = ABSTRACT