Retrieves the equipment parent item for a given item.

This method traverses up the hierarchy of items starting from a given itemId, until it finds the equipment parent item. In other words, if you pass it an item id of a suppressor, it will traverse up the muzzle brake, barrel, upper receiver, gun, nested backpack, and finally return the backpack Item that is equipped.

It's important to note that traversal is expensive, so this method requires that you pass it a Map of the items to traverse, where the keys are the item IDs and the values are the corresponding Item objects. This alleviates some of the performance concerns, as it allows for quick lookups of items by ID.