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/circuits/mod.rs

@@ -4,4 +4,5 @@ use ark_ff::Field;
 
 pub mod cyclefold;
 
-pub type ConstraintF<C> = <<C as CurveGroup>::BaseField as Field>::BasePrimeField;
+// CF represents the constraints field
+pub type CF<C> = <<C as CurveGroup>::BaseField as Field>::BasePrimeField;