Allow filtering resources in nested blocks by context

[eballeste]

As a UX/QOL feature, it would be amazing if we could force resources to only show options that are based off of parent resource settings.

For example:
for a featured collection + top 3 featured products module:
if a parent block (or section) has a collection field, allow us to set a nested block with a product field setting that will only show products from that collection, something like:

{
  "type": "product",
  "id": "featured_product"
  "label": "Featured product",
  "filter_by": "{{ closest.collection }}"
}

this way merchants do not have to go through a list of unrelated products