Ensure legacy_asn1_ctrl_to_param can handle MDs not in the OBJ database

Ensure legacy_asn1_ctrl_to_param can handle MDs not in the OBJ database

The legacy_asn1_ctrl_to_param implementation of
ASN1_PKEY_CTRL_DEFAULT_MD_NID calls EVP_PKEY_get_default_digest_name()
which returns an mdname. Previously we were using OBJ_sn2nid/OBJ_ln2nid
to lookup that name in the OBJ database. However we might get an md name
back that only exists in the namemap, not in the OBJ database. In that
case we need to check the various aliases for the name, to see if one of
those matches the name we are looking for.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/13899)