Fix performance regression introduced by UCP support.

 Changes to add the Oracle UCP support feature (JBJCA-1410) introduced a performance regression. Replicated in JSE8 and JSE9.
This needs to be fixed to eliminate sources of exceptions during execution.

The optimal solution is to cache the lookup of the virtual method. To make subsequent calls optimal. Both when successful (>=JSE9) or not (JSE8).
Swap out the Reflection implementation with MethodHandle. The up-to date technique for virtual method invocation. Allowing the whole execution pipeline to be fully optimized by HotSpot. Whereas Reflection is an dead end for HotSpot.

The caching implementation should ensure the MethodHandle reference should remain reachable between leases of ManagedConnection.

The implementation should work consistently for JSE8 and >=JSE9.