Moves disfiguration to be handled by the head instead of the mob itself (#94948)

## About The Pull Request
TRAIT_DISFIGURED and physical disfiguration are now handled by the head
bodypart rather than being on the mob itself. This is mostly for
internal purposes, but it does mean that:
- Players can now perform plastic surgery on torn off heads.
- Disfigured mobs' heads keep their face hidden, and when attached to a
different body won't magically get repaired and vice versa, attaching a
new head to a disfigured corpse no longer disfigures it.
- Robotic (and other non-huskable) heads no longer become disfigured
from husking
- Also in the rare case of grafting a head torn off from a husk onto
another body, they no longer permanently turn into an Unknown. (lol)

## Why It's Good For The Game

Saner code, we generally want limb-specific behaviors to be on limbs
themselves and not on the mob. Also yeah that one weird edge case.
~~Husks are next on the chopping block~~

## Changelog
🆑
qol: Plastic surgery can now be done on detached heads.
refactor: Refactored how disfiguration is handled to be stored on head's
side
fix: Robotic (and other non-huskable) heads no longer become disfigured
from husking
fix: Attaching a head from a husk to a different body no longer
permanently turns them into an Unknown.
/🆑

code/game/objects/structures/headpike.dm

@@ -44,7 +44,7 @@
 	update_appearance()
 
 /obj/structure/headpike/update_name()
-	name = "[victim.real_name] on a [spear.name]"
+	name = "[victim.get_face_name()] on a [spear.name]"
 	return ..()
 
 /obj/structure/headpike/update_overlays()