Implement Nova's NIFS.Verify circuits (with CycleFold) (#11)

* Implement Nova's NIFS.Verify circuits (with CycleFold)

- Add circuit for NIFS.Verify on the main curve to check the folded `u`
  & `x`
- Add circuit for NIFS.Verify on the CycleFold's auxiliary curve to
  check the folded `cm(E)` & `cm(W)`
- Add transcript.get_challenge_nbits
- Add tests for utils::vec.rs

* replace bls12-377 & bw6-761 by pallas & vesta curves (only affects tests)

We will use pallas & vesta curves (for tests only, the non-tests code
uses generics) for the logic that does not require pairings, and while
Grumpkin is not available
(https://github.com/privacy-scaling-explorations/folding-schemes/issues/12).

* update links to papers to markdown style

src/folding/nova/mod.rs

@@ -5,6 +5,7 @@ use ark_std::{One, Zero};
 
 use crate::pedersen::{Params as PedersenParams, Pedersen};
 
+pub mod circuits;
 pub mod nifs;
 
 #[derive(Debug, Clone, Eq, PartialEq)]
@@ -14,6 +15,7 @@ pub struct CommittedInstance<C: CurveGroup> {
     pub cmW: C,
     pub x: Vec<C::ScalarField>,
 }
+
 impl<C: CurveGroup> CommittedInstance<C> {
     pub fn empty() -> Self {
         CommittedInstance {