canio: Run background tasks while waiting for message reception

[jepler]

While I don't have enough information to determine if this is what affected the original reporter, I had an stm32f405 feather that readily reproduced the problem. I eventually discovered that the problem affected me only when I had a program that used canio and was spending all its time waiting in common_hal_canio_listener_receive for a packet that never arrived. This was due to missing background task & interrupt key checking in the blocking loop in common_hal_canio_listener_receive.

I added the extra code to both esp32-s2, samd and st code, but only tested stm32f405 feather.

Closes: #5004

[microdev1]

Thanks @jepler. Changes look good, just one question, was esp32s2 left out on purpose?
Also, I am not sure if this is related to #5004.

[jepler]

No, I really do believe this is the fix for #5004. I'll check esp32-s2 and of course get the build fixed.

[microdev1]

Also, I am not sure if this is related to #5004.

The reason why I came to that conclusion is because the issue author listed code.py as empty.
I don't mind closing the issue now as it can always be re-opened later if the issue persists.

[jepler]

issue author listed code.py as empty.

I overlooked this detail. perhaps there are two problems, then.

[microdev1]

LGTM! 👍

[dhalbert]

@jepler Fine to merge?

[Chad-Krause]

How does this code work? Does it use asyncio? Is there an example I can see?