ecdhtest.c: move co-factor ECDH KATs to evptests

move NIST SP800-56A co-factor ECDH KATs from ecdhtest.c to evptests.txt

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3218)