[Jersey-Client] Support for custom implementations of concurrency - Feature Request

In the current implementation of Jersey if we have a ThreadLocal and use async the only way to pass the ThreadLocal variables from the concurrent thread to async thread is with **Invocation.Builder.property(String name, Object value)**, if we have a ClientRequestFilter, We can get this information in async Thread with ClientRequestContext.getProperty(String name), per example:

## Call in original Thread
`Future future = webTarget.path("/api/account/123")
.request(MediaType.APPLICATION_JSON_VALUE)
.property("requestContextHolder", RequestContextHolder.getRequestAttributes())
.async()
.get(Account.class);`

## Filter that runs in async Thread
`public void filter(final ClientRequestContext requestContext) throws IOException {
RequestAttributes requestAttributes = (RequestAttributes) requestContext.getProperty("requestAttributes");
}`

This way solves the problem, but is not elegant for a case that we need to set this information for different APIs calls.
For this case would be nice if Jersey have a way to be more extensible, like [HystrixConcurrencyStrategy](https://netflix.github.io/Hystrix/javadoc/com/netflix/hystrix/strategy/concurrency/HystrixConcurrencyStrategy.html), where we can define in one place what to copy from current thread to async thread or a place where we can fill ClientRequestContext with all the properties that we need in Async Thread for this request.