Clothing fallback (#18258)

* Clothing fallback

Makes clothing have a fallback in the event of a custom species file not having the appropriate icon state.

* some logging

* testing

* swap all unit tests to use icon_exists

* Update poster_tests.dm

* Update clothing_tests.dm

* Update cosmetic_tests.dm

* Update robot_tests.dm

* whoop

* upgrades people, upgrades

* port these

* Update _atom.dm

* adjust all these

* Update clothing.dm

* TRUEFALSE

code/modules/mob/living/carbon/human/update_icons.dm

@@ -345,7 +345,7 @@ GLOBAL_LIST_EMPTY(damage_icon_parts) //see UpdateDamageIcon()
 				base_icon.MapColors(rgb(tone[1],0,0),rgb(0,tone[2],0),rgb(0,0,tone[3]))
 
 		//Handle husk overlay.
-		if(husk && ("overlay_husk" in cached_icon_states(species.icobase)))
+		if(husk && icon_exists(species.icobase, "overlay_husk"))
 			var/icon/mask = new(base_icon)
 			var/icon/husk_over = new(species.icobase,"overlay_husk")
 			mask.MapColors(0,0,0,1, 0,0,0,1, 0,0,0,1, 0,0,0,1, 0,0,0,0)

code/modules/mob/living/silicon/pai/pai_vr.dm

@@ -83,12 +83,12 @@
 
 	// Unfortunately not all these states exist, ugh.
 	else if(vore_fullness && !resting)
-		if("[chassis]_full[fullness_extension]" in cached_icon_states(icon))
+		if(icon_exists(icon, "[chassis]_full[fullness_extension]"))
 			icon_state = "[chassis]_full[fullness_extension]"
 		else
 			icon_state = "[chassis]"
 	else if(vore_fullness && resting)
-		if("[chassis]_rest_full[fullness_extension]" in cached_icon_states(icon))
+		if(icon_exists(icon, "[chassis]_rest_full[fullness_extension]"))
 			icon_state = "[chassis]_rest_full[fullness_extension]"
 		else
 			icon_state = "[chassis]_rest"