Avoid serialization/deserialization of StreamElement value

[je-ik]

Call to

  StreamElement elem = StreamElement.upsert(..., serialized(value));
  Object value = elem.getParsed().get()

causes unnecessary serialization and deserialization of value. We can extend StreamElement.upsert() with the (optional) deserialized object that will be set to parsed cache and prevent deserialization upon retrieval.