As the int types defined in include/zephyr/types.h are typdef's we
utilize a Kconfig option (LEGACY_ZEPHYR_INT_TYPES) to enable/disable
the support for them. By default to LEGACY_ZEPHYR_INT_TYPES not
being enabled and add an explicit test to ensure the types continue to
function until removed in the future.
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>