Apply Promotion only if it gives the best possible value to the customer

Describe your bug or feature request.

It should be possible to choose on the Promotion level whether the promotion should only apply if it gives the best value among available Promotions.

The simple scenarios should be covered by ✨ Introduce a new event for filtering the available promotions for an order Fixed but for more complex scenarios we need for the order of promotions to evaluate in the context of order items.

Example from this comment: ✨ Introduce a new event for filtering the available promotions for an order Fixed
Merchant has Promotion A with the amount-based offer of 30 USD and Promotion B with the percentage-based offer of 30%. Given both promotions apply to the Order and both have the compatibility set to none one should be able to determine which promotion gives a better value to the customer in the context of the order item. Therefore if the Unit Price of the Order Item is lower than 100 USD Promotion A gives a better value, but if the Unit Price of the Order Item is greater than 100 USD then Promotion B gives a better value to the customer. When the Unit Price is equal to 100 USD the discount value is equal for Promotion A and Promotion B therefore one with the lower weight applies.