Deprecate / Remove MicroProfile RESTClient implementation

The implementation for MicroProfile RESTClient should not have been added to the RESTEasy project, and should be removed to reduce maintenance/support burdens across projects.

The current, and up to date, implementation is present in WildFly Swarm.

In the future there will be a common implementation that RESTEasy might want to take advantage of, but until then it's best that this code is removed.

I believe the current code is mostly present in https://github.com/resteasy/Resteasy/tree/master/resteasy-client/src/main/java/org/jboss/resteasy/client/microprofile