lib: Move crypto library tests to Runtime Testing menu

Currently the kconfig options for the crypto library KUnit tests appear
in the menu:

    -> Library routines
      -> Crypto library routines

However, this is the only content of "Crypto library routines".  I.e.,
it is empty when CONFIG_KUNIT=n.  This is because the crypto library
routines themselves don't have (or need to have) prompts.

Since this usually ends up as an unnecessary empty menu, let's remove
this menu and instead source the lib/crypto/tests/Kconfig file from
lib/Kconfig.debug inside the "Runtime Testing" menu:

    -> Kernel hacking
      -> Kernel Testing and Coverage
        -> Runtime Testing

This puts the prompts alongside the ones for most of the other lib/
KUnit tests.  This seems to be a much better match to how the kconfig
menus are organized.

Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20260322032438.286296-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

lib/Kconfig.debug

@@ -3058,6 +3058,8 @@ config HW_BREAKPOINT_KUNIT_TEST
 
 	  If unsure, say N.
 
+source "lib/crypto/tests/Kconfig"
+
 config SIPHASH_KUNIT_TEST
 	tristate "Perform selftest on siphash functions" if !KUNIT_ALL_TESTS
 	depends on KUNIT