[GSS][7.1.z] Support for AssertionConsumerServiceUrl in Saml Adapter subsystem

keycloak-saml.xml supports configuration of an assertionConsumerServiceURL attribute for the SP part.
AS7-EAP6 or Wildfly SAML Adapter subsystem don't support this attribute.
It would be better to support this as well.
Those that need to set that attribute are now forced to use the keycloak-saml.xml file in each deployment where they should have the choice whether or not they want to use the subsystem configuration, which makes it transparent for the deployment archive(s).