Enable documents filtering by inline array fields

[islamaliev]

currently we allow filtering of documents by related objects:

query {
  Author(filter: {
    books: {rating: {_gt: 3}}
  }) {
    name
    books {
      name
    }
  }
}

But there is no way we can do it for inline arrays like [String].
One of the ideas is to introduce new operators _all, _any and _none that should count number of filter matches for every element in the array:

query {
  Author(filter: {
    genres: {_any: {_eq: "Horror"}}
  }) {
    name
  }
}

query {
  Author(filter: {
    publishedYears: {_all: {_gt: 2010}}
  }) {
    name
  }
}

Alternatively (or additionally) we can integrate aggregates into filters with their own filters within:

query {
  Author(filter: {
    _count(books: { filter: {
      rating: {_gt: 3}
    }}): {_eq: 2}
  }) {
    name
  }
}

This would allow us to specify exactly how many matching elements should be in the array.

Tangentially related idea:
it might be also useful to request indexes of matching elements into the array and potentially afterwards use them to manipulate the array.