Add `path` to Normalization API

[samdenty]

Given a query for a list of objects:

query {
  something {
    items(limit: 1) {
      name
    }
  }
}

And we want to normalize an Item to the index by which it appears in items.

normalization: {
  identifier(item) {
    return item.__typename + index
  }
}

One possible way of implementing it, is a second getParent / path argument:

normalization: {
  identifier(item, { getParent, path }) {
// path ==
[
  { key: "0",         args: null,         data: { name: "" }                             },
  { key: "items",     args: { limit: 1 }, data: [{ name: "" }]                           },
  { key: "something", args: null,         data: { items: [{ name: "" }] }                },
  { key: null,        args: null,         data: { something: { items: [{ name: "" }] } } },
];


	const { key, args, parent } = getParent(item)
    
    // key == "0"
    // args == null
    // parent == [{name:""}]
    
    return item.__typename + key // aka the index
  }
}

path being an array of the keys / args / data to the root of the response

and getParent being a function which accepts any item, and returns the key/args of the item, along with the parent item (which can be fed back in)