Add set_sigalgs to ssl_client / get_peer_signature_nid to set key exchange params

[mxsasha]

Reference:
https://docs.openssl.org/1.1.1/man3/SSL_CTX_set1_sigalgs/
https://docs.openssl.org/1.1.1/man3/SSL_get_peer_signature_nid/

Some thoughts:

• My C is rusty I have never written CPython before, but I think it's correct.
• The first commit in this PR uses SSL_set1_sigalgs_list() which just takes a string. The final implementation with explicit typing seemed nicer to me.
• Not sure whether this is the right place for these new values/enums, or best naming. Definitely might be a bit sloppy to have non-EC in OpenSslEvpPkeyEnum which lives in ephemeral_key_info.py
• There's some duplication between nassl_SSL_set1_sigalgs and nassl_SSL_set1_groups now. I tried to extract it to python_utils, but felt it was not saving much. Might not be worth it at this time.

[nabla-c0d3]

Thank you ! This was merged as part of #124