test: Move the unit tests to their own menu

Make all unit tests selectable as a menu of test suites instead of just
sitting in the top-level menu individually.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Acked-by: Simon Glass <sjg@chromium.org>

test: dm: Move the dm tests over to the ut command

Unify the command for running unit tests further by moving the "dm test"
command over to "ut dm".

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Acked-by: Simon Glass <sjg@chromium.org>

test: Generalize the unit test framework

Separate the ability to define tests and assert status of test functions
from the dm tests so they can be used more consistently throughout all
tests.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

dm: test: Add a Kconfig file

Add a file to control driver model test features.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Masahiro Yamada <yamada.m@jp.panasonic.com>