Also updates Bulletproofs from C to not be length prefixed, yet rather
have Rust calculate their length.
Corrects an error in key_gen where self was blamed, instead of the
faulty participant.
Adds helper functions to verify and, on failure, blame, which move an
unwrap from callers into multiexp where it's guaranteed to be safe and
easily verified to be proper.
Closes https://github.com/serai-dex/serai/issues/10.
Saves ~8% during FROST key gen, even with dropping a vartime for a
constant time (as needed to be secure), as the new batch verifier is
used where batch verification previously wasn't. The new multiexp API
itself also offered a very slight performance boost, which may solely be
a measurement error.
Handles most of https://github.com/serai-dex/serai/issues/10. The blame
function isn't binary searched nor randomly sorted yet.
