Add utils::vec & pedersen modules (#5)
- utils::vec module: port a mix of vec utils from nova-study, multifolding-poc and protogalaxy-poc repos
- pedersen.rs: Pedersen commitment module
- other:
- update FoldingScheme trait interface: rm rng, update internal types naming as agreed in today's call
- update Cargo.toml dev-dependencies imports, since bn254 - grumpkin is not ready yet, use bls12-377 - bw6-761 curve cycle
- transcript module: add absorb_point method