feat: core contracts

[parketh]

Summary

This PR adds:

• the core PrivateBank and MerkleTree contracts
• merkle + snark proof circuits
• verifier
• smart contract tests for the above
• deployment scripts
• deploy logs

Test plan

see the README for full install instructions (requires circom and snarkjs)

# install deps
yarn

# download ptau file
yarn setup

# build circuits + contracts
yarn build

# run test
yarn test

test runner: