Add safe Rust wrappers for ML-KEM-768 and ML-KEM-1024

[lbaquerofierro]

Adds safe Rust wrappers around BoringSSL's ML-KEM (FIPS 203) key encapsulation, covering both ML-KEM-768 and ML-KEM-1024 parameter sets.

• Key generation, encapsulation, and decapsulation
• Seed-based private key storage and restoration
• Public key derivation, serialization, and validation
• Wipes private key material from memory on drop
• Tests for roundtrip, implicit rejection, debug redaction, and validation

[cjpatton]

It should be possible to deduplicate this code using traits.

pub trait Kem {
    /// Note: SEED_BYTES and SHARED_SECRET_BYTES are the same for all ML-KEM parameters
    const PUBLIC_KEY_BYTES: usize;
    const CIPHERTEXT_BYTES: usize;
    type PublicKey;
    type PrivateKey;
}

pub trait KemOps: Kem {
    fn generate() -> (Kem::PublicKey, Kem::PrivateKey) { ... }
    fn encapsulate .. 
    fn decapsulate ...
}