Move the KDF code for CMS DH key agreement into an EVP_KDF object.
There are 2 specifications for X9.42 KDF. This implementation uses DER for
otherinfo which embeds the KDF loop counter inside the DER object.
Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/8898)
