refactor: test going back to MSM in fold

src/provider/pedersen.rs

@@ -280,8 +280,10 @@ where
   // combines the left and right halves of `self` using `w1` and `w2` as the weights
   fn fold(L: &Self, R: &Self, w1: &E::Scalar, w2: &E::Scalar) -> Self {
     debug_assert!(L.ck.len() == R.ck.len());
-    let ck_curve: Vec<E::GE> =
-      zip_with!(par_iter, (L.ck, R.ck), |l, r| *l * w1 + *r * w2).collect();
+    let ck_curve: Vec<E::GE> = zip_with!(par_iter, (L.ck, R.ck), |l, r| {
+      E::GE::vartime_multiscalar_mul(&[*w1, *w2], &[*l, *r])
+    })
+    .collect();
     let mut ck_affine = vec![<E::GE as PrimeCurve>::Affine::identity(); L.ck.len()];
     E::GE::batch_normalize(&ck_curve, &mut ck_affine);