lib/Kconfig.debug: change KUnit tests to default to KUNIT_ALL_TESTS

lib/Kconfig.debug: change KUnit tests to default to KUNIT_ALL_TESTS

This is in line with Documentation/dev-tools/kunit/style.rst.
Some of these tests predate that so they don't follow this convention.

With this and commit b0841b51cac9 ("kunit: arch/um/configs: Enable
KUNIT_ALL_TESTS by default"), kunit.py will now run these tests by
default. This hopefully makes it easier to run and maintain the tests.
If any of these were to start failing, people would notice much quicker.

Note: this commit doesn't update LINEAR_RANGES_TEST since that would
select its dependency (LINEAR_RANGES). We don't want KUNIT_ALL_TESTS
to enable anything other than test kconfigs.

Signed-off-by: Daniel Latypov <dlatypov@google.com>
Reviewed-by: David Gow <davidgow@google.com>
Reviewed-by: Nico Pache <npache@redhat.com>
Acked-by: Nico Pache <npache@redhat.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>