Introducing taskpools, a small lightweight ARC/ORC threadpool

[elcritch]

Brilliant! I'm literally just looking into how to do an event/thread pool type 
of problem in embedded (Zephyr in this case). The sync/spawn types are pretty 
nice syntax and much better than easier to use than the system built-in work 
queues. I don't want to run ORC, so this might work nicely. Thanks!