Change the ASN1 variant of x942kdf so that it can test acvp data.

Change the ASN1 variant of x942kdf so that it can test acvp data.

This 'special' way of specifying the data should only be used for testing
purposes. It should not be used in production environments.
ACVP passes a blob of DER encoded data for some of the fields rather
than passing them as separate fields that need to be DER encoded.

Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/14077)