Audits wash/cleaning signals + refactors wash() to ensure no needless mob updates occur (#91259)

## About The Pull Request

This has the potential to create a lot of needless mob updates which is
not great. Now should only update a mob's clothing if it was actually
washed.

This PR

1) ensures that all wash() procs return a bitflag.
2) ensures that `wash()` proccalls which result in expensive operations
like icon updates only do so when it is necessary

## Why It's Good For The Game

Updating mob sprites is expensive, and doing it when nothing has been
changed is bad.

## Changelog

Nothing really player facing

code/game/objects/items.dm

@@ -1428,6 +1428,8 @@
 // Update icons if this is being carried by a mob
 /obj/item/wash(clean_types)
 	. = ..()
+	if(!.) // we don't need mob updates when the item was already clean
+		return
 	if(ismob(loc))
 		var/mob/mob_loc = loc
 		mob_loc.update_clothing(slot_flags)