[FEAT] Be able to get information about the exception thrown in case of failure

[mickaelandrieu]

As point in https://github.com/loveOSS/resiliency/issues/61, we are not able to know which exception is responsible of a failure and so on we are not able to open/close manually our circuit breaker according to the exception.

As the current architecture doesn't allows to setup the related exception of a circuit breaker, the only chance we get is to add a new event and allow developer to manually setup new conditions of open/close decision.

// ThrowableEvent
function listener(Failed $event) {
    $exception = $event->getException();

   if ($exception->getException() instanceof HttpNotFoundOrWhatever) {
       $uri = $event->getService()->getURI();
       $circuitBreaker = $event->getCircuitBreaker();
       $circuitBreaker ->isolate($uri);
       // OR
       $circuitBreaker ->reset($uri);
   }
};

This could be improved but I don't see how without introducing a big breaking change, what I don't want as I'm not involved in PHP projects anymore.