samples|tests: drivers: flash: Add support for "jedec,mspi-nor" devices

Extend several flash samples and tests so that they can also be used
with "jedec,mspi-nor" devices.
Add configurations needed for the nrf54h20dk/nrf54h20/cpuapp target.

Signed-off-by: Andrzej Głąbek <andrzej.glabek@nordicsemi.no>