Native image improvements to MP REST Client for Quarkus

Quarkus needs the following changes to the MP REST Client implementation for improving native image generation:

• When SSL is disabled, switch to using the `URLConnectionEngine` as the default engine still requires SSL classes which are not present in a native image
• Ability to define a custom `ResteasyProviderFactory` so that only the providers that are required for an application are loaded by RESTEasy. This enables the unused providers to be removed from the generated native image.