Add a cart order status indicating that a payment is being processed

[mattbrailsford]

Originally discussed here: umbraco/Umbraco.Commerce.PaymentProviders.Mollie#1

add another status to the carts status dropdown of "Processing" which could list carts that have had their payment initialized and possibley a "Failed" statuses if they have been sat in that state for a specific period.

This would give you an indication of orders that are mid payment / stuck...