Some tests need more work.
* The adc test builds, but isn't set up correctly for the 2350 hardware
yet.
* The multicore and gpio_multicore tests only work from flash,
seems to be a probe-rs issue.
* The i2c and flash tests also only works from flash, these are probably
bugs but I don't have time to run them down now.
* The 2350 gpio test skips anything with pull downs. I think these fail
because of E9.
The float, bootsel, cyw43, and ethernet tests don't have 2350 equivalents.
There's no reason to use the float romfuncs, use the FPU.
Bootsel as a button isn't supported on the 2350 yet.
The wifi and eth tests don't have appropriate hardware.
The i2c test has also been tweaked to run on one core.
this reports errors at the same location the blocking uart would, which
works out to being mostly exact (except in the case of overruns, where
one extra character is dropped). this is actually easier than going
nuclear in the case of errors and nuking both the buffer contents and
the rx fifo, both of which are things we'd have to do in addition to
what's added here, and neither are needed for correctness.
the rp uart receive fifo is 32 entries deep, so the 31 byte test data
fits into it without needing any buffering. extend to 48 bytes to fill
the entire fifo and the 16 byte test buffer.
