Send with ack is blocking for the rfm9x library

[thetazero]

While we are awaiting a uhf ack, nothing else is running

[thetazero]

While it doesn't completely block execution now, it still takes up a considerable amount of time.
With each send calling tx_done something like 226 times, nearly completely taking over the flow of execution from everything else.

[thetazero]

interrupts in circuitpython not well supported