[Forwardport] Cart-Sales-Rule-with-negated-condition-over-special-price-does-not-work-for-configurable-products. Use configurable product`s children for shopping cart rules validation for cases when attribute exists for children only (E.g. special_price)

[nmalevanec]

Original Pull Request

#16342

Use configurable product`s children for shopping cart rules validation
for cases when attribute exists for children only (E.g. special_price)

Description

Fixed Issues (if relevant)

1. Cart Sales Rule with negated condition over special_price does not work for configurable products #14020 Cart Sales Rule with negated condition over special_price does not work for configurable products

Manual testing scenarios

1. Enable the special_price for promo rule conditions:
   1. Stores > Attributes > Product
   2. Search for and edit special_price
   3. Storefront Properties: Use for Promo Rule Conditions: Yes
   4. Save
2. create new cart sales rule:
   1. Marketing > Cart Price Rules
   2. Add New Rule:
      1. Rule name = "Special Price Test"
      2. Website: select all
      3. Customer Groups: select all
      4. Coupon: "Specific Coupon"
      5. Coupon Code: "special"
      6. Actions: Discount Amount: "10"
      7. Actions: Apply the rule only to cart items matching the following conditions: "if ALL of these conditions are FALSE": "Special Price greater than 0.01"
      8. Leave all other fields to their defaults and save
3. In the front end, add a the child product of a configurable product to the cart, such that the child product has a special price set. This product should be the only one in the cart.
4. "View and Edit Cart" > "Apply Discount Code": special

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[magento-engcom-team]

Hi @nmalevanec. Thank you for your contribution
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