Co-authored-by: Pratyush Mishra <pratyushmishra@berkeley.edu>

* Implement `ToBitsGadget` for `UInt8` and `Vec<UInt8>`
* Add `kary_or` function to `Boolean`.

* adds alloc constant to AllocGadget

* fmt

* fmt

* more alloc constant impls

* fmt

* even more impls

* fixes type

* fixes alloc_constant in gm17

* uses alloc_constant from field gadget in group gadgets

* fmt

* handle most comments

* Add mnt6_753 curve
Generalize mnt6 curve model

* Add mnt4 curves

* Use resampled generators

* Calculate correct G2 cofactors

* Add fields to r1cs-std

* Add pairings

* Improve reusing of Fq/Fr among MNT curves

* Add instantiations of curves
Fix Fp6_2over3
Rebase code to current master

* Add test for recursive NIZK proof verification

* Address comments in PR

* Improve test case and port to GM17
Also fix a minor bug in to_field_vec

Co-Authored-By: Pratyush Mishra <pratyushmishra@berkeley.edu>

* refactor(r1cs-std/boolean): expose enforcing value less than functionality

* fix(r1cs-std/boolean): ensure num_bits is calculated correctly from the arg

* feat(primitives/blake2s): allow creating Blake2s with custom params