Clean up domain mode logic related to remoting subsystem worker configuration

Once WFCORE-6472 is done, see if there's any funky code related to remoting endpoint / worker configuration and domain mode. A long time ago this configuration area was refactored and there may be some crufty code related to supporting the old style in a mixed domain. But we don't support such old hosts in a mixed domain any longer so there may be an oppportunity for some cleanup / simplification.

It's possible there isn't.

This issue was inspired by https://github.com/wildfly/wildfly-core/pull/5563/commits/23dffc4847672ecbb1a577e0cebe755e4fda9a6c#diff-a77b580614385b89990fe9e3eb09f84edd9e5e516ba610f8366dcdbb91a58481L229-R229 which led me to look at that code, which led to the feeling there may be some possibility for cleanup.

In particular some of the stuff in WorkerThreadPoolVsEndpointHandler related to domain mode seemed suspicious.