Use NIDs instead of the old TLSv1.2 sigalgs hash and sig ids

Use NIDs instead of the old TLSv1.2 sigalgs hash and sig ids

We had an extra layer of indirection in looking up hashes and sigs based
on sigalgs which is now no longer necessary. This removes it.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2157)