[ML-KEM] Match mainline APIs

[jschneider-bensch]

This PR ports over some of the APIs that are provided for ML-KEM in mainline libcrux, namely:

• The KEM-trait API. This is currently broken, because this branch depends on a different version of libcrux-secrets than the libcrux-traits crate.
• The PQCP "packed" APIs. We don't have the unpacked APIs here, so we also can't provide those for PQCP.
• The (de-)serialization of public keys and ciphertexts with tls_codec

The PR does not port the incremental API.

[jschneider-bensch]

Blocked on #117 getting merged, which updates the C extraction scripts.