Elevates (almost all) inventory variables from /carbon to /human (#96955)

## About The Pull Request

Moves all inventory slots but handcuffs/legcuffs (as those can be used
by xenos) from ``/carbon`` onto ``/human``, as xenos do not use any of
those inventory slots, only leaving them in use by humans. Their
presence on ``/carbon`` is an artifact of times when monkeys weren't
humans, and some of the slots had to be shared by all carbons.
In some places I've used ``get_item_by_slot`` rather than swapping
checks to ``ishuman`` for simplicity's sake, in some places it might not
be the most optimal solution but in cases like help act any other
solution would require a refactor of the whole (massive) proc.

## Why It's Good For The Game

Cleaner/more sensible code, one step closer to fully datumized
inventories.

## Changelog
🆑
refactor: Moved a lot of human-specific inventory code onto human mobs,
report if inventories break!
/🆑

code/_onclick/hud/screen_objects/alert.dm

@@ -1162,13 +1162,13 @@
 	if(!.)
 		return
 
-	var/mob/living/carbon/carbon_owner = owner
+	var/mob/living/carbon/human/human_owner = owner
 
-	if(!carbon_owner.can_resist() || !carbon_owner.shoes)
+	if(!human_owner.can_resist() || !human_owner.shoes)
 		return
 
-	carbon_owner.changeNext_move(CLICK_CD_RESIST)
-	carbon_owner.shoes.handle_tying(carbon_owner)
+	human_owner.changeNext_move(CLICK_CD_RESIST)
+	human_owner.shoes.handle_tying(human_owner)
 
 /atom/movable/screen/alert/shoes/untied
 	name = "Untied Shoes"