Add mapping linter to check for duplicate machinery stacked on same t…

…ile (#79394)

This has happened quite a few times in the past and it'd be a good idea
to have a linter catch this common mistake. After digging through the
Python code for the mapping linter, it appears the linter wasn't
correctly identifying two duplicate objects. I tweaked the code to fix
this.

tools/maplint/lints/multiple_machinery.yml

@@ -0,0 +1,4 @@
+/obj/machinery:
+  banned_neighbors:
+    /obj/machinery:
+      identical: true

tools/maplint/source/lint.py

@@ -66,7 +66,13 @@ def __init__(self, typepath, data = {}):
 
     def matches(self, identified: Content, neighbor: Content):
         if self.identical:
-            return neighbor == identified
+            if identified.path != neighbor.path:
+                return False
+
+            if identified.var_edits != neighbor.var_edits:
+                return False
+
+            return True
 
         if self.typepath is not None:
             if self.typepath.matches_path(neighbor.path):