tests:basic: Add cSHAKE test vectors.

* tests/basic.c (check_one_md): Extend with customization N and S.
(check_one_md_multi): Likewise.
(check_digests): Add test vectors for GCRY_MD_CSHAKE128 and
GCRY_MD_CSHAKE256.

Test vectors are from:

https://csrc.nist.gov/CSRC/media/Projects/
Cryptographic-Standards-and-Guidelines/
documents/examples/cSHAKE_samples.pdf

• GnuPG-bug-id: T6637
• Co-authored-by: Falko Strenzke <falko.strenzke@mtg.de>
• Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>