Only Trigger a Process if it's not Already Running Excluding a Final Call

NOTE: If the last signal comes in while the second process is running, then it is not triggered a final time. See the restart-process... example for how to kill and restart a secondary process to deal with that. (Another thing worth figuring out is how to send a final cleanup type signal, but I don't need that at the moment.)

GOAL: send multiple signals at an interval that set an in progress flag that gets turned off after a delay.

GOAL: Incoming signals don't block. The processing keeps happening in the background and is only triggered when it's freed up.