Additional checks for fragments added in category tree

[rogyar]

Description

For category products request on an attempt to add a fragment for checking an implementation (product type) the system throws the fatal error. The example of request:

{
  category(id: 14) {
    id
    name
    products {
      items {
        sku
        ... on ConfigurableProduct {
          variants {
            product {
              sku
            }
          }
        }
      }
    }
  }
}

The fix removes the InlineFragment nodes from category tree processing.

Fixed Issues (if relevant)

#85

Manual testing scenarios

• Create a configurable product with child products
• Assign the configurable product to a category with some [category_id]
• Execute the following request:

{
  category(id: category_id) {
    id
    name
    products {
      items {
        sku
        ... on ConfigurableProduct {
          variants {
            product {
              sku
            }
          }
        }
      }
    }
  }
}

• You should see the category and products info instead of the fatal error.

[magento-cicd2]

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