Add tests for set_image.

[Gadgetoid]

This change attempts to test for the Inky wHAT set_image display issue mentioned in #182 and tries to determine if the internal buffer is set correctly.

Testing

If you want to test this branch, make sure you're running in the virtual environment to which you installed Inky and run:

pip install git+https://github.com/pimoroni/inky@patch-inky-resolution-test --force-reinstall

That should replace your version of the Inky library with the experimental version on this branch!

[stonehippo]

@Gadgetoid this fix works on my wHAT, since it removes the funky flipped cols and rows.

[BryanH]

Confirmed this fix works on my wHAT (examples/logo.py), however the SPI error remains:

Detected Yellow wHAT
/home/pi/.virtualenvs/pimoroni/lib/python3.11/site-packages/inky/inky.py:254: UserWarning: SPI: Cannot disable chip-select!
  warnings.warn("SPI: Cannot disable chip-select!")

/boot/firmware/config.txt contains:

[all]
dtoverlay=i2c1
dtoverlay=i2c1-pi5
dtoverlay=spi0-0cs

[pipplo]

Just posting here to confirm that it fixes the issues on the gpiod branch I was having with my inkyWhat display