Ability to set structure element query params to element queries

[brandonkelly]

It should be possible to set structure element query params to element queries, similar to relatedTo.

Specifically, these params:

• ancestorOf
• descendantOf
• siblingOf
• prevSiblingOf
• nextSiblingOf
• positionedBefore
• positionedAfter

Twig example:

{% set entries = craft.entries()
  .section('services')
  .level(1)
  .type('serviceCategory')
  .ancestorOf(
    craft.entries()
      .level(2)
      .type('serviceDetail')
  )
  .all() %}

GraphQL example:

entries(
  section: "services"
  level: 1
  type: "serviceCategory"
  ancestorOf: {
    level: 2
    type: "serviceDetail"
  }
) {
  ...
}