Need results stored on relevant objects, to avoid unnecessary calculations

Description

Previously, calculators recalculated prices and taxes even if an order had no changes or if the changes did not affect results. This practice is inefficient, especially when using an external tax service. It also creates problems with old orders, deleted products, expired promotions, new promotions, etc. Now if an order has no changes that affect results, no recalculations take place. Instead, the previously-calculated values are returned. Another improvement is that a new property is available to store TaxCategoryId for a line item. So, even if a product is deleted, Commerce retains tax information for processing the order later.