Fix benchmark compilation and add benchmarks for Edwards curves

curve-benches/src/curves/ed_on_bls12_381.rs

@@ -0,0 +1,18 @@
+use rand::SeedableRng;
+use rand_xorshift::XorShiftRng;
+use std::ops::{AddAssign, MulAssign, SubAssign};
+
+use ark_ec::ProjectiveCurve;
+use ark_ed_on_bls12_381::{fq::Fq, fr::Fr, EdwardsAffine as GAffine, EdwardsProjective as G};
+use ark_ff::{
+    biginteger::{BigInteger256 as FrRepr, BigInteger256 as FqRepr},
+    BigInteger, Field, PrimeField, SquareRootField, UniformRand,
+};
+
+mod g {
+    use super::*;
+    ec_bench!(G, GAffine);
+}
+
+f_bench!(Fq, Fq, FqRepr, FqRepr, fq);
+f_bench!(Fr, Fr, FrRepr, FrRepr, fr);