Add a simple test intended primarily for checking the nRF temperature
sensor in its nrfs variant but intentionally was made generic enough
that it should be usable with other temperature sensors (after just
providing an overlay) and could be helpful in development of new
temperature sensor drivers, and possibly extended then if needed.
Signed-off-by: Andrzej Głąbek <andrzej.glabek@nordicsemi.no>
