DOCS: Fix provider-mac.pod and the docs of our implementations

DOCS: Fix provider-mac.pod and the docs of our implementations

The idea being that doc/man7/provider-mac.pod is for provider authors,
while provider users find the documentation for each implementation in
doc/man7/EVP_MAC-*.pod, the documentation of parameters wasn't quite
aligned.  This change re-arranges the parameter documentation to be
more aligned with this idea.

Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/14380)