Core: fix single player item links (#3721)

* fix single player item links

* Make a variable and fix weird spacing

* use advancement instead of classification

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Co-authored-by: Exempt-Medic <60412657+Exempt-Medic@users.noreply.github.com>

BaseClasses.py

@@ -342,6 +342,8 @@ class MultiWorld():
             region = Region("Menu", group_id, self, "ItemLink")
             self.regions.append(region)
             locations = region.locations
+            # ensure that progression items are linked first, then non-progression
+            self.itempool.sort(key=lambda item: item.advancement)
             for item in self.itempool:
                 count = common_item_count.get(item.player, {}).get(item.name, 0)
                 if count: