OpenVPN error codes, SSL_get_peer_signature_* funcs, and first patch file

[smittals2]

Issues

CryptoAlg-2477
CryptoAlg-2478

Description of changes:

1. Added three new aliases for AES-128-GCM, AES-192-GCM, and AES-256-GCM as required by OpenVPN
2. Added an error and function code. Error code points to our equivalent of the OpenSSL PKCS12_R_MAC_VERIFY_FAILURE error
3. Added SSL_get_peer_signature_nid and SSL_get_peer_signature_type_nid. No new state is stored for these in the SSL connection.
4. Generated a patch file to use OpenVPNs internal ASSERT function instead of OpenSSL_assert, SSL_get_ciphers instead of SSL_get1_supported_ciphers, and point SSL_get_peer_tmp_key to SSL_get_server_tmp_key (which we define as a no-op)
5. Added pkcs8.h to doc.config

Call-outs:

The patch file is temporary and will likely change with future PRs

Testing:

1. SSL_get_peer_signature_nid and SSL_get_peer_signature_type_nid are tested in a TLS 1.2 connection (with renegotiation) and in a TLS 1.3 connection (with mTLS configured to test both the client and server side).

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 85.18519% with 4 lines in your changes missing coverage. Please review.

Project coverage is 78.15%. Comparing base (98735a2) to head (50de7b3).

Files	Patch %	Lines
ssl/ssl_lib.cc	80.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1584      +/-   ##
==========================================
- Coverage   78.16%   78.15%   -0.01%     
==========================================
  Files         562      562              
  Lines       94683    94710      +27     
  Branches    13575    13579       +4     
==========================================
+ Hits        74008    74022      +14     
- Misses      20082    20093      +11     
- Partials      593      595       +2     

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[geedo0]

LGTM, just some style nits to fix.