Specify type & code via config

[t1]

Add an option to configure the mapping of some built-in exceptions, e.g. org.eclipse.microprofile.faulttolerance.exceptions.CircuitBreakerOpenException to status code 503 Service Unavailable.

And there should be a default config for as many built-in exceptions as possible. See https://github.com/microprofile-extensions/jaxrs-ext/blob/master/configurable-exception-handler/README.md for a good starting point.