Use MethodHandles to access AWS Request metadata

[mcculls]

Reduces the need to maintain a side-table of metadata by using method handles to access named (public) getters.

[tylerbenson]

Much better solution.

[richardstartin]

I consolidated these in to GenericClassValue last week, so that you could write

  private static final ClassValue<RequestAccess> REQUEST_ACCESS =
      GenericClassValue.of(new Function<Class<?>, RequestAccess>() {
        @Override
        public RequestAccess apply(final Class<?> requestType) {
          return new RequestAccess(requestType);
        }
      });

and optionally factor out a function to construct an instance from a class parameter and drop the helper class, or

  private static final ClassValue<RequestAccess> REQUEST_ACCESS = GenericClassValue.of(RequestAccess::new);

and drop the helper class when we drop JDK7.