message: Implement StructureTracker functions
diff: namespace
  {
  + void addItemToList(const StructureTracker::StructureItem& structureItem, StructureTracker::StructureItemList& list)
  + {
  + for (const auto& item : list)
  + {
  + if (item.id == structureItem.id)
  + {
  + return;
  + }
  + }
  + list.push_back(structureItem);
  + }
  };
  void StructureTracker::addUnlockedSurfaceStructure(const StructureItem& structureItem)
  {
  -
  + addItemToList(structureItem, mUnlockedSurfaceStructures);
  }
  void StructureTracker::addUnlockedUndergroundStructure(const StructureItem& structureItem)
  {
  -
  + addItemToList(structureItem, mUnlockedUndergroundStructures);
  }
  