ML-DSA: Signing works across all parameter sets.

[xvzcf]

• The contents of the two files serialize.rs and deserialize.rs have been moved into a module called encoding, serialization and deserialization functions are now grouped together according to what they act upon.
• The KATs have been updating to also store a signing_randomness value that is used during signing
• I now use tuple structs to hold the signing key, verification key, and signature, as well as another struct that groups the signing and verification key tuple structs

[franziskuskiefer]

lgtm with a few nits

[franziskuskiefer]

Thanks