selftests/lkdtm: Enable various testable CONFIGs

Add a handful of LKDTM-testable features that depend on certain CONFIGs
so that they are visible in logs for CI systems that run the selftests.
Others could be added, but may be seen as having too high a trade-off
for general testing.

Cc: kernelci@groups.io
Suggested-by: Guillaume Tucker <guillaume.tucker@collabora.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210623203936.3151093-9-keescook@chromium.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tools/testing/selftests/lkdtm/config

 CONFIG_LKDTM=y
+CONFIG_DEBUG_LIST=y
+CONFIG_SLAB_FREELIST_HARDENED=y
+CONFIG_FORTIFY_SOURCE=y
+CONFIG_HARDENED_USERCOPY=y
+# CONFIG_HARDENED_USERCOPY_FALLBACK is not set
+CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT=y