Formal Proof for UltraPlonk Pedersen Hash

[suyash67]

A formal collision resistance proof for the ultraplonk pedersen hash (based on the merkle damagard construction) is pending. Opening this issue so that we don't forget this.

Code:

barretenberg/cpp/src/aztec/stdlib/hash/pedersen/pedersen_plookup.cpp

Line 140 in 3f40133

point<C> pedersen_plookup<C>::merkle_damgard_compress(const std::vector<field_t>& inputs, const field_t& iv)

Spec: https://hackmd.io/@aztec-network/ryDVeaT6d?type=view#The-UltraPlonk-pedersen-hash

[suyash67]

We no longer use Merkle-Damgard construction in barretenberg, so closing this.