Update to new benchmarking framework (#126)

mnt4_298/benches/mnt4_298.rs

@@ -0,0 +1,15 @@
+use ark_algebra_bench_templates::*;
+use ark_mnt4_298::{
+    fq::Fq, fq2::Fq2, fr::Fr, Fq4, G1Projective as G1, G2Projective as G2, MNT4_298,
+};
+
+bench!(
+    Name = "MNT4_298",
+    Pairing = MNT4_298,
+    G1 = G1,
+    G2 = G2,
+    ScalarField = Fr,
+    G1BaseField = Fq,
+    G2BaseField = Fq2,
+    TargetField = Fq4,
+);