Add generic EVP_PKEY_METHOD for EVP_MACs

The MAC EVP_PKEY implementations are currently implemented for each
MAC.  However, with the EVP_MAC API, only one such implementation is
needed.

This implementation takes into account the differences between HMAC
and CMAC implementations, and observes that all other current MAC
implementations seem to follow the HMAC model.

Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/7393)