This patch had been already merged in rLabe6dddff99b: T89411: Order refund amounts must be stored, not calculated properties because it's blocking T84408: Subscriptions and payments

Adds the following columns to the Order:

• refunded_at datetime which copied value from the latest Transaction.refunded_at;
• refunded which stores a sum of all Transaction.amount_refunded;
• tax_refunded which stores a sum of Order.tax_rate applies to each of Transaction.amount_refunded, if non-zero tax was stored with the order.