Make response available on error in rest client

[rober710]

Responses cannot be read if the HTTP status is not in the 2xx range and you request that the response is converted to a specific type, like when calling

httpClient.target("https://example.com/endpoint").request(MediaType.APPLICATION_JSON_TYPE).get(MyBean.class);

In this case, an exception is thrown, but it contains a DummyResponse instance that doesn't give access to the Response object.
Being able to read the response from the server in case of error is extremely valuable in some cases, as it may contain useful information about the problem. Most REST APIs return this information as a JSON object that can be parsed, and the contents examined to see custom error status codes or passing the error message to the user, for example.

This PR sets the response in the exception object, without creating a new field for it, as implementing ResteasyReactiveClientProblem should prevent the server from trying to read the response.