dhtest: Add testcase for EVP_PKEY_CTX_set_dh_nid
dhtest: Add testcase for EVP_PKEY_CTX_set_dh_nid

And a negative testcase for EVP_PKEY_CTX_set_dhx_rfc5114

Reviewed-by: Matt Caswell <1fa2ef4755a9226cb9a0a4840bd89b158ac71391@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17498)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl