This is a follow on to https://github.com/wildfly/wildfly/pull/13597/files

EndpointService's isElytronSecurityDomain and isLegacySecurityDomain are checking if things are present by doing MSC service lookups. Generally that's unreliable; but it works in this case because all subsystems install their services before deployment processing begins, and EndpointService is part of deployment processing.

Still, the services that are being looked up are associated with a capability. So these methods can just use CapabilityServiceSupport.hasCapability to see if that capability is present.

Semi-related, in various places related to security domain integration EndpointService is using different strategies for creating a ServiceName for the security-related service. Some of those would be eliminated by the main change I discuss above. The others should consolidate on using CapabilityServiceSupport. getCapabilityServiceName.