* feat: start hypernova nimfs verifier

* refactor: change where nimfs verifier lives

* feat: `EqEvalGadget` for computing `eq(x, y)`

* refactor: rename to `utils.rs`

* feat: implement a `VecFpVar` struct, representing a vector of `FpVar`s

* refactor: extract a `sum_muls_gamma_pows_eq_sigma` function to make circuit tests easier

* feat: implement a `SumMulsGammaPowEqSigmaGadget` to compute the first term of the sum of section 5, step 5

* refactor: update gadget name and method name to match `sum_muls_gamma_pows_eq_sigma`

* fix: update method call

* refactor: remove usage of `GammaVar`

Co-authored-by: arnaucube <root@arnaucube.com>

* refactor: move hypernova circuit related types and methods into `src/folding/hypernova/circuits.rs`

* refactor: remove all of `GammaVar` wrapper

* chore: update type to `&[F]`

* refactor: update from `new_constant` to `new_witness`

* fix: actual file deletion

* refactor: remove `VecFpVar` struct

* chore: update comment doc

* refactor: extract a `sum_ci_mul_prod_thetaj` function for testing

* feat: `test_sum_ci_mul_prod_thetaj_gadget` passing

* refactor: update docs and add a helper `get_prepared_thetas` function

* refactor: clearer arg name

* fix: clippy typing

* chore: correct latex comments

* refactor: remove unncessary `get_prepared_thetas` fn

* feat: test passing for rough first pass on `ComputeCFromSigmasAndThetasGadget`

* chore: add additional doc comments

* chore: add `#[allow(clippy::too_many_arguments)]`

* refactor: make gadget generic over a curve group

* chore: clippy fixes

* chore: correct latex in doc comment

* refactor: refactor `sum_muls_gamma_pows_eq_sigma` and `sum_ci_mul_prod_thetaj` in `ComputeCFromSigmasAndThetasGadget`

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Co-authored-by: arnaucube <root@arnaucube.com>

* Port HyperNova's multifolding from https://github.com/privacy-scaling-explorations/multifolding-poc adapting and refactoring some of its methods and structs.

Note: adapted mle.rs methods from dense to sparse repr.

Co-authored-by: George Kadianakis <desnacked@riseup.net>

* HyperNova: move CCS struct outside of LCCCS & CCCS

HyperNova nimfs: move CCS structure outside of LCCCS & CCCS, to avoid
carrying around the whole CCS and duplicating data when is not needed.

Also add feature flags for the folding schemes.

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Co-authored-by: George Kadianakis <desnacked@riseup.net>