Change the aztec-nr Address derivation

[nventuro]

The AztecAddress is currently computed as poseidon2(pub_keys_hash, partial_address). This needs to change to:

let h: Field = poseidon2(pub_keys_hash, partial_address);
let mut maybe_address: Point = h * G + Ivpk_m;
if maybe_address.y > Y_HALF_RANGE { maybe_address = -maybe_address }
let address: Field = maybe_address.x; // wrap in AztecAddress

Note that this means we can no longer derive an address from just the pub keys hash and the partial address, we now also need the Ivpk_m (which part of the preimage of the pub keys hash, and we should know it in all flows in which we also know the pub keys hash).