* Allow for priority to be set on event emitters
* Add payment event emitters
* add new actions/status to checkout state context
* implement event emitters in payment data context
* refactor checkout state context to use new actions in event emitters
* refactor checkout processor to handle new event emitters
* fix type-defs for registered payment methods
* register observer for cheque payment method integration
* add inline todo
* fix sort
* fix tests and add test for priority usage in event emitters
* remove todo and just add explanatory comment
* condense sort logic
* lowercase test description
* abstract emitter callback to reduce code
* don’t process passed in errors if it’s undefined
* improve error response expectation for payment processing event observer
* Hook up checkout validation with context
* Make sure hasValidationErrors is up to date in onCheckoutProcessing
* Move validation check inside CheckoutProcessor's processCheckout
* Make sure all checkout form fields have a unique ID
* Don't clear checkout context errors in shipping context
* Move CheckoutProcessor to the top so scrollToTop works
* Do not disable Place Order Button if there are errors
* Split checkValidation and processCheckout in Checkout Provider
* Refactor event emitter to use Maps
* Save payment method errors to validation context
* Show an notice when a payment method has an error
* Make sure JS errors during payment are displayed
* Remove error notice when payment method doesn't return an error anymore
* Make sure payment methods know if shipping and billing addresses are the same
* Make sure checkout is only processed if payment methods didn't fail
* Make sure state input also has an id
* Clear input and select errors on unmount
* Pass id to CountryInput and StateInput
* Fix function name
* Add missing default context values
* Move onCheckoutCompleteError effect to CheckoutBlock
* Remove conditional from shipping setHasError
* Rename and move existing checkout provider to checkout-state provider.
This allows us to re-use the interface exposed on this provider for cart and checkout blocks.
* refactor checkout provider to implement the new checkout state provider.
* Add Cart provider and export
* fix type-defs
* fix editor context provider and ensure all `isEditor` checks come from this provider
* fix type definition
* implement cart provider