All arguments to pin.irq are converted from keyword-only to positional, and
can still be specified by keyword so it's a backwards compatible change.
The default value for the "trigger" arg is changed from 0 (no trigger)
to rising+falling edge.
Previously they used historical "pyb" affix causing confusion and
inconsistency (there's no "pyb" module in modern ports; but people
took esp8266 port as an example, and "pyb" naming kept proliferating,
while other people complained that source structure is not clear).
