Implement canonical Falcon512 signature

With the support for precompiles added to Miden VM, we could also support the canonical Falcon512 signature scheme (which we should probably call something like `Falcon512_Sha512`). As the first step for adding this support, we should implement wrappers for this scheme in this repo.

The implementation should expose interfaces similar to ECDSA/EdDSA schemes (e.g., we probably need to have the ability to sign the "pre-hashed" message), and would also probably want to keep the deterministic signing.

One of the questions we'll need to answer is which underlying implementation to use. The options are: the canonical C implementation, or the Rust implementation from [here](https://github.com/pornin/rust-fn-dsa).

Another question is whether we want to update the way we compute public key commitments as otherwise, I believe, both the canonical version and our RPO versions would end up with the same public key commitments (which may or may not be a problem).