[Experimental] Improve conversion functionality for events

[fjtirado]

Currently users are forced to add an outputAs method to access the first element of the collection

 listen(
                          "waitHumanReview",
                          to().one(
                                  consumed("org.acme.newsletter.review.done")
                                      .extensionByInstanceId("instanceid")))
                      .outputAs((Collection<?> events) -> events.iterator().next()),
                  // The engine sees the incoming JsonNode, sees this task expects
                  // HumanReview.class,
                  // and natively deserializes it for you before executing the lambda!
                  switchWhenOrElse(
                      h -> HumanReview.NEEDS_REVISION.equals(h.status()),
                      "humanEditorAgent",
                      "sendNewsletter",
                      HumanReview.class)

It would be nice if they can just write

   listen(
                      "waitHumanReview",
                      to().one(
                              consumed("org.acme.newsletter.review.done")
                                  .extensionByInstanceId("instanceid"))),
                  // The engine sees the incoming JsonNode, sees this task expects
                  // HumanReview.class,
                  // and natively deserializes it for you before executing the lambda!
                  switchWhenOrElse(
                      h -> HumanReview.NEEDS_REVISION.equals(h.status()),
                      "humanEditorAgent",
                      "sendNewsletter",
                      HumanReview.class),