Move lib/test_uuid.c to lib/tests/uuid_kunit.c and convert it to use KUnit.

This change switches the ad-hoc test code to standard KUnit test cases. 
The test data remains the same, but the verification logic is updated to
use KUNIT_EXPECT_* macros.

Also remove CONFIG_TEST_UUID from arch/*/configs/* because it is no longer
used.  The new CONFIG_UUID_KUNIT_TEST will be automatically enabled by
CONFIG_KUNIT_ALL_TESTS.

[lukas.bulwahn@redhat.com: MAINTAINERS: adjust file entry in UUID HELPERS]
  Link: https://lkml.kernel.org/r/20251217053907.2778515-1-lukas.bulwahn@redhat.com
Link: https://lkml.kernel.org/r/20251215134322.12949-1-sakamo.ryota@gmail.com
Signed-off-by: Ryota Sakamoto <sakamo.ryota@gmail.com>
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@redhat.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: David Gow <davidgow@google.com>
Cc: Andriy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: Lukas Bulwahn <lukas.bulwahn@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>