Add worker test setup

[lok52]

Closes #83

Updates:

• Add test-flow-generator tool. It allows you to generate any transaction flow with pre-calculated proofs and signatures using a json file. Flows can also be made of independent transactions meaning that each transaction uses the same merkle root for SNARK proofs.
• Add several worker tests (in file zp-relayer/test/worker-tests) covering functionality added in recent releases. Each test runs in an independent environment with clear node's state (with deployed pool contracts only) and clear local state. Tests use zp-relayer/test/flows/flow_independent_deposits_5.json file with pre-generated flow using test-flow-generator. You can generate your own flow to test different scenarios if needed. Also, you can change test env variables in test.env file if needed.
• Priority for sentTxQueue jobs is now calculated as tx_nonce+1 because 0 priority is undefined in bullmq.

NOTES:

• ZK transactions and SNARK proofs in test-flow-generator are calculated in local browser environment (launched automatically using puppeteer) using libzkbob-rs-wasm-web package.
• Contracts are deployed using lok52/zkbob-contracts docker image with tweaked Env.s.sol file where relayer and token minter addresses are changed (bobMinter = 0x90F8bf6A479f320ead074411a4B0e7944Ea8c9C1, zkBobRelayer = 0x22d491Bde2303f2f43325b2108D26f1eAbA1e32b).
• Also, there some useful utility functions prepared in zp-relayer/test/utils.ts, e.g. you can enable/disable mining on a node, mine blocks manually, drop transactions from mempool, etc.
• To run tests you should have a locally installed docker-compose