Create a credit messaging area handler for use on the cart and checkout Views

In order to place credit messaging beneath the order total on the cart page, we should create a Views area handler similar to the area handler used to render the cart order’s total price field. The area handler will need to accept an order as an argument and then render the messaging div / load the JS library.

The configuration for the area handler should let the merchant specify the “Placement” as being either “Cart” or “Payment.” If they’re adding this to the commerce_cart_form View, it would be “Cart”, and if to the commerce_checkout_order_summary, it would be “Payment.” Either way, it should properly set the “amount” to the order total so the messaging can use the right numbers.