Some webshops work with only a billing address because products need to be picked up from a location. If this is the case, the billing address should be filled in, and valid before a payment method can be used. This is already the case with payment methods native to Magento 2, but not with this Adyen module. Because of this, orders could be placed using Adyen payment methods, without adding an address at all. This extra check fixes this.

Refs #662.
Co-authored-by: cyattilakiss <42297201+cyattilakiss@users.noreply.github.com>