* NIFI-9543: add bring-to-front functionality to labels
* NIFI-9543: update zIndex changes to persist after shutdown
* NIFI-9543: remove commented code
* NIFI-9543: update flow comparator and snippet to account for zIndex
* NIFI-9543: changed add function to sort labels when a new label is added
* NIFI-9543: remove unnecessary call to position
* NIFI-9543: only register difference if zIndex is not default value
* NIFI-9543: add null checks to prevent primitive Long
This closes#5765