THIS CHANGE WAS REVERTED. In order to represent a payment method configuration entity as multiple brands, use plugin derivatives to represent one payment method (Payment\Method) plugin as multiple brands. See https://www.drupal.org/node/2357543.
Payment method plugins can now represent themselves as multiple brand options to payers by implementing PaymentProcessingInterface::brandOptions(). This method replaces the configured generic payment method entity titles from 7.x-1.x. All plugins that extend \Drupal\payment\Plugin\payment\method\Base have a single label that defaults to the payment method entity label, unless this behavior is overridden. Basic payment methods retain the configurable brand label, which works identically to the generic title from 7.x-1.x.
