As we have for `RestClientBuilderImpl`, see https://github.com/resteasy/Resteasy/blob/master/resteasy-client-microprofile-base/src/main/java/org/jboss/resteasy/microprofile/client/RestClientBuilderImpl.java#L72, it would be good to have the same ability with `ResteasyClientBuilderImpl`.

For Quarkus we customize the providers that are registered, and when a user choose to use the JAX-RS `ClientBuilder` we currently don't have a way to guarantee the providers are appropriately set.