feature: support for ML-DSA handshake signatures

[lrstewart]

Release Summary:

Resolved issues:

related to #5257

Description of changes:

The last of the logic necessary to negotiate ML-DSA. I add the signature schemes, fix bugs in the auth selection logic that prevent ML-DSA from being chosen, and update TLS1.3 CertVerify to properly initialize the hash. After this PR, s2n-tls can handshake using ML-DSA.

Call-outs:

This PR is still trying to keep ML-DSA invisible to customers. There will be one last PR that makes it visible by adding documentation, updating "default_pq", adding integ tests, and adding a new value to the public s2n_tls_signature_algorithm enum. That's when we can consider ML-DSA done and announce it as available for use.

Testing:

New self-talk handshake tests.

Also, I manually tested a handshake against Openssl-3.5. Openssl command:

> openssl s_server -accept 8888 -cert tests/pems/mldsa/ML-DSA-44.crt -key tests/pems/mldsa/ML-DSA-44-seed.priv

s2n-tls command and output:

> s2nc localhost 8888 --ciphers "test_all_tls13" -i
libcrypto: AWS-LC 1.49.1
CONNECTED:
Handshake: NEGOTIATED|FULL_HANDSHAKE|MIDDLEBOX_COMPAT
Client hello version: 33
Client protocol version: 34
Server protocol version: 34
Actual protocol version: 34
Server name: localhost
Curve: x25519
Cipher negotiated: TLS_AES_128_GCM_SHA256
Server signature negotiated: None+None
Early Data status: NOT REQUESTED
Wire bytes in: 6718
Wire bytes out: 307
s2n is ready
Connected to localhost:8888

Notice that the "None" signature negotiated is because ML-DSA hasn't been added to s2n_tls_signature_algorithm yet.

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