Smash the singular Ciphersuite trait into multiple

This helps identify where the various functionalities are used, or rather, not
used. The `Ciphersuite` trait present in `patches/ciphersuite`, facilitating
the entire FCMP++ tree, only requires the markers _and_ canonical point
decoding. I've opened a PR to upstream such a trait into `group`
(https://github.com/zkcrypto/group/pull/68).

`WrappedGroup` is still justified for as long as `Group::generator` exists.
Moving `::generator()` to its own trait, on an independent structure (upstream)
would be massively appreciated. @tarcieri also wanted to update from
`fn generator()` to `const GENERATOR`, which would encourage further discussion
on https://github.com/zkcrypto/group/issues/32 and
https://github.com/zkcrypto/group/issues/45, which have been stagnant.

The `Id` trait is occasionally used yet really should be first off the chopping
block.

Finally, `WithPreferredHash` is only actually used around a third of the time,
which more than justifies it being a separate trait.

---

Updates `dalek_ff_group::Scalar` to directly re-export
`curve25519_dalek::Scalar`, as without issue. `dalek_ff_group::RistrettoPoint`
also could be replaced with an export of `curve25519_dalek::RistrettoPoint`,
yet the coordinator relies on how we implemented `Hash` on it for the hell of
it so it isn't worth it at this time. `dalek_ff_group::EdwardsPoint` can't be
replaced for an re-export of `curve25519_dalek::SubgroupPoint` as it doesn't
implement `zeroize`, `subtle` traits within a released, non-yanked version.
Relevance to https://github.com/serai-dex/serai/issues/201 and
https://github.com/dalek-cryptography/curve25519-dalek/issues/811#issuecomment-3247732746.

Also updates the `Ristretto` ciphersuite to prefer `Blake2b-512` over
`SHA2-512`. In order to maintain compliance with FROST's IETF standard,
`modular-frost` defines its own ciphersuite for Ristretto which still uses
`SHA2-512`.

processor/signers/Cargo.toml

@@ -26,8 +26,7 @@ zeroize = { version = "1", default-features = false, features = ["std"] }
 
 blake2 = { version = "0.11.0-rc.0", default-features = false, features = ["alloc"] }
 ciphersuite = { path = "../../crypto/ciphersuite", default-features = false, features = ["std"] }
-dalek-ff-group = { path = "../../crypto/dalek-ff-group", default-features = false, features = ["std"] }
-frost = { package = "modular-frost", path = "../../crypto/frost", default-features = false }
+frost = { package = "modular-frost", path = "../../crypto/frost", default-features = false, features = ["ristretto"] }
 frost-schnorrkel = { path = "../../crypto/schnorrkel", default-features = false }
 
 scale = { package = "parity-scale-codec", version = "3", default-features = false, features = ["std"] }

processor/signers/src/batch/mod.rs

@@ -3,8 +3,7 @@ use std::collections::HashSet;
 
 use blake2::{digest::typenum::U32, Digest, Blake2b};
 use ciphersuite::group::GroupEncoding;
-use dalek_ff_group::Ristretto;
-use frost::dkg::ThresholdKeys;
+use frost::{dkg::ThresholdKeys, curve::Ristretto};
 
 use scale::Encode;
 

processor/signers/src/cosign/mod.rs

@@ -1,7 +1,6 @@
 use core::future::Future;
 
-use dalek_ff_group::Ristretto;
-use frost::dkg::ThresholdKeys;
+use frost::{dkg::ThresholdKeys, curve::Ristretto};
 
 use scale::Encode;
 use serai_primitives::Signature;

processor/signers/src/lib.rs

@@ -7,9 +7,8 @@ use std::collections::HashMap;
 
 use zeroize::Zeroizing;
 
-use ciphersuite::{group::GroupEncoding, Ciphersuite};
-use dalek_ff_group::Ristretto;
-use frost::dkg::ThresholdKeys;
+use ciphersuite::{group::GroupEncoding, *};
+use frost::{dkg::ThresholdKeys, curve::Ristretto};
 
 use serai_primitives::Signature;
 use serai_validator_sets_primitives::{Session, SlashReport};

processor/signers/src/slash_report.rs

@@ -1,7 +1,6 @@
 use core::{marker::PhantomData, future::Future};
 
-use dalek_ff_group::Ristretto;
-use frost::dkg::ThresholdKeys;
+use frost::{dkg::ThresholdKeys, curve::Ristretto};
 
 use serai_primitives::Signature;
 use serai_validator_sets_primitives::Session;

processor/signers/src/wrapped_schnorrkel.rs

@@ -5,9 +5,9 @@ use std::{
 
 use rand_core::{RngCore, CryptoRng};
 
-use dalek_ff_group::Ristretto;
 use frost::{
   dkg::{Participant, ThresholdKeys},
+  curve::Ristretto,
   FrostError,
   algorithm::Algorithm,
   sign::*,