* Move r1cs and ccs to standalone folders

* Simplify type bounds of SparseMatrixVar

* Implement `EquivalenceGadget` trait for `FpVar` and `NonNativeUintVar`.

Together with the existing `MatrixGadget` and `VectorGadget`, we can now use the same logic for checking R1CS satisfiability of `R1CSVar` both natively and non-natively.

* Simplify trait bounds

* Implement `ArithGadget` for `R1CSMatricesVar` and `CCSMatricesVar`

* `PedersenGadget::commit` now takes slices as input

* Structs for proofs and auxiliary values in protogalaxy

* `u` in LCCCS should be `z[0]`

* `Inputize` trait

* Generic decider circuits

* Verifier should check the commitments in committed instances

* Update the comments according to the new docs

* Fix examples

* Add `DeciderEnabledNIFS::fold_group_elements_native` to wrap code for folding commitments

* Fix incorrect endian

* Format

* Get rid of `unwrap` when possible