Allow batching of deferred fields nested in multidimensional lists

[IvanGoncharov]

Given a query:

{
  list {
    innerList {
      ... @defer {
        foo
      }
    }
  }
}

Response:

[
  {
    "data": {
      "list": [
        { "innerList": [{}] },
        { "innerList": [{}, {}] },
        { "innerList": [{}, {}, {}] },
      ]
    },
    "hasNext": true
  },
  {
    "incremental": [
      {
        "path": ["list", [], "innerList", []],
        "data": [
          [{ "foo": 1 }], 
          [{ "foo": 2 }, { "foo": 3 }], 
          [{ "foo": 4 }, { "foo": 5 }, { "foo": 6 }]
        ]
      }
    ],
    "hasNext": false,
  }
]

Motivation:

1. Prevent intentional or unintentional DoS attack but still defer data instead of inlining
2. Allow query rewriting to achieve full deduplication
3. Server optimization, especially for a case where a data loader is used