* Remove isExpressPaymentMethodActive and paymentStatus.isDoingExpressPayment from the payment store
* Remove uneccessary paymentStatuses key from the payments store
* Rename payment-method-data-context to payment-event-context and tidy up types and things
* Rename uses of PAYMENT_METHOD_DATA_STORE_KEY to PAYMENT_STORE_KEY
* Rename __internalInitializePaymentMethodDataStore and unsubscribeInitializePaymentMethodDataStore
* Rename unsubscribeInitializePaymentMethodDataStore