Merge branch 'more_self_referential_inventory' into 'master'

Make objects know what inventory they're in.

Inspired by the mess that is Wintertide's special on hit. As of !693, combat tables and their objects is now a two-way association. This MR aims to make the object-actor association similarly two way. Items should know where they are and who is holding them, which is accomplished by setting `o.in_inven`, which holds `o.in_inven.actor` and `o.in_inven.id`. This prevents requiring obnoxious searches of inventories for an item in question, and prevents potential search collisions (as `define_as` is not a perfect identifier).

**This MR is save safe, although any behavior reliant on this will not apply to objects without changing their position in inventories.**

See merge request !802

@@ -313,6 +313,8 @@ function _M:onAddObject(o, inven_id, item)
 			end
 		end
 	end
+	
+	o.in_inven = {actor = self, id = inven_id}
 end
 
 --- Called upon removing an object
@@ -323,6 +325,7 @@ function _M:onRemoveObject(o, inven_id, item)
 		end
 	end
 	o.carried = nil
+	o.in_inven = nil
 end
 
 --- Called upon dropping an object

@@ -68,8 +68,9 @@ It is said the Conclave created this weapon for their warmaster during the dark
 				local Map = require "engine.Map"
 
 				-- special_on_hit doesn't know what item triggered it, so find it
-				local self, item, inven_id = who:findInAllInventoriesBy("define_as", "LONGSWORD_WINTERTIDE")
-				if not self or not who:getInven(inven_id).worn then return end
+				local self = combat.self
+				local inven_id = self and self.in_inven and self.in_inven.id
+				if not self or not inven_id or not who:getInven(inven_id).worn then return end
 
 				if who.turn_procs.wintertide_sword then return end