Add Ed25519 to FROST and remove expand_xmd for elliptic_curve's

Doesn't fully utilize ec's hash2curve module as k256 Scalar doesn't have 
FromOkm for some reason. The previously present bigint reduction is 
preserved.

Updates ff/group to 0.12.

Premised on https://github.com/cfrg/draft-irtf-cfrg-frost/pull/205 being 
merged, as while this Ed25519 is vector compliant, it's technically not 
spec compliant due to that conflict.

coins/monero/src/tests/frost.rs

@@ -1,76 +0,0 @@
-use rand::rngs::OsRng;
-
-use sha2::Sha512;
-
-use dalek_ff_group as dfg;
-use frost::{
-  Curve,
-  algorithm::Hram,
-  tests::{curve::test_curve, schnorr::test_schnorr, vectors::{Vectors, vectors}}
-};
-
-use crate::frost::{Ed25519, Ed25519Internal};
-
-#[test]
-fn frost_ed25519_curve() {
-  test_curve::<_, Ed25519>(&mut OsRng);
-}
-
-#[test]
-fn frost_ed25519_schnorr() {
-  test_schnorr::<_, Ed25519>(&mut OsRng);
-}
-
-// Not spec-compliant, as this shouldn't use wide reduction
-// Is vectors compliant, which is why the below tests pass
-// See https://github.com/cfrg/draft-irtf-cfrg-frost/issues/204
-//type TestEd25519 = Ed25519Internal<Sha512, false>;
-// If this is kept, we can remove WIDE
-type TestEd25519 = Ed25519Internal<Sha512, true>;
-
-#[derive(Copy, Clone)]
-struct IetfEd25519Hram {}
-impl Hram<TestEd25519> for IetfEd25519Hram {
-  #[allow(non_snake_case)]
-  fn hram(R: &dfg::EdwardsPoint, A: &dfg::EdwardsPoint, m: &[u8]) -> dfg::Scalar {
-    TestEd25519::hash_to_F(
-      b"",
-      &[&R.compress().to_bytes(), &A.compress().to_bytes(), m].concat()
-    )
-  }
-}
-
-#[test]
-fn frost_ed25519_vectors() {
-  vectors::<TestEd25519, IetfEd25519Hram>(
-    Vectors {
-      threshold: 2,
-      shares: &[
-        "929dcc590407aae7d388761cddb0c0db6f5627aea8e217f4a033f2ec83d93509",
-        "a91e66e012e4364ac9aaa405fcafd370402d9859f7b6685c07eed76bf409e80d",
-        "d3cb090a075eb154e82fdb4b3cb507f110040905468bb9c46da8bdea643a9a02"
-      ],
-      group_secret: "7b1c33d3f5291d85de664833beb1ad469f7fb6025a0ec78b3a790c6e13a98304",
-      group_key: "15d21ccd7ee42959562fc8aa63224c8851fb3ec85a3faf66040d380fb9738673",
-
-      msg: "74657374",
-      included: &[1, 3],
-      nonces: &[
-        [
-          "8c76af04340e83bb5fc427c117d38347fc8ef86d5397feea9aa6412d96c05b0a",
-          "14a37ddbeae8d9e9687369e5eb3c6d54f03dc19d76bb54fb5425131bc37a600b"
-        ],
-        [
-          "5ca39ebab6874f5e7b5089f3521819a2aa1e2cf738bae6974ee80555de2ef70e",
-          "0afe3650c4815ff37becd3c6948066e906e929ea9b8f546c74e10002dbcc150c"
-        ]
-      ],
-      sig_shares: &[
-        "4369474a398aa10357b60d683da91ea6a767dcf53fd541a8ed6b4d780827ea0a",
-        "32fcc690d926075e45d2dfb746bab71447943cddbefe80d122c39174aa2e1004"
-      ],
-      sig: "2b8d9c6995333c5990e3a3dd6568785539d3322f7f0376452487ea35cfda587b".to_owned() +
-           "75650edb12b1a8619c88ed1f8463d6baeefb18d3fed3c279102fdfecb255fa0e"
-    }
-  );
-}

coins/monero/src/tests/mod.rs

@@ -1,4 +1 @@
-#[cfg(feature = "multisig")]
-mod frost;
-
 mod clsag;