Updates rp2 port to always resume from idle within 1ms max.
When rp2 port went tickless the behaviour of machine.idle() changed as
there is no longer a tick interrupt to wake it up every millisecond. On a
quiet system it would now block indefinitely. No other port does this.
See parent commit for justification of why this change is useful.
Also adds a test case that fails without this change.
This work was funded through GitHub Sponsors.
Signed-off-by: Angus Gratton <angus@redyak.com.au>
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