* factor out editor preview data for saved payment methods to previews
* add missing imports lost in rebase
* use editorcontext to provide preview data to payment method context
* remove unused `activePaymentMethod` prop in CheckoutProvider and PaymentMethodDataProvider
* don't set the preview saved card as the default
* fix js error with cart in editor - fix EditorContext, pass previewData:
- editor context preview prop has changed;
- update cart to pass { previewCart } in previewData prop
- correctly destructure cart from previewData in useStoreCart hook
- correct typedefs
- EditorProvider props.previewData - now just Object
- similar for EditorDataContext
- correct default for activePaymentMethod state - empty string as before
* preselect 'use a new payment method' in checkout block editor preview
* update unit tests for changes to editor context
* remove calculating as a checkout status (making it separate)
* include checkout is calculating for determining whether to flip payment status to process
* only change payment method state for status changes if needed
* fix reducer for shipping state
* include checkoutIsCalculating for determining whether to show validation errors in checkout block
* change where currentStatus is defined
* fix bug with saved payment method option
* Add saved-payment-method options handling and improve payment method registration initialization
* add server side exposure of saved customer payment methods
* fix reducer for express payment method state
* fix default for customerPaymentMethods
Rua Haszard
Darren Ethier