Support prove command api

[0xmad]

• Support prove command cli for coordinator service
• Make sure all inputs are sanitized
• Download zkey files for the service
• Support coordinator key encryption to prevent storing private data inside the service
• Support prove configuration params

[kittybest]

To add more details for "Make sure all inputs are sanitized":
make sure the private key input is valid: take public from contract https://github.com/privacy-scaling-explorations/maci/blob/dev/contracts/contracts/Poll.sol#L25
create keypair from coordinator private key, check public key match

this is because the error generated by using wrong private key is hard to understand, and I am not sure if the same error also displayed in other cases, so I think it's better to check the keypairs first.

An unexpected error occurred:

AssertionError [ERR_ASSERTION]: false == true
    at genMaciStateFromContract (/home/user/Documents/maci/contracts/ts/genMaciState.ts:156:9)
    at processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async SimpleTaskDefinition.action (/home/user/Documents/maci/contracts/tasks/runner/prove.ts:127:25)
    at async Environment._runTaskDefinition (/home/user/Documents/maci/node_modules/.pnpm/[email protected][email protected][email protected]/node_modules/hardhat/src/internal/core/runtime-environment.ts:359:14)
    at async Environment.run (/home/user/Documents/maci/node_modules/.pnpm/[email protected][email protected][email protected]/node_modules/hardhat/src/internal/core/runtime-environment.ts:192:14)
    at async main (/home/user/Documents/maci/node_modules/.pnpm/[email protected][email protected][email protected]/node_modules/hardhat/src/internal/cli/cli.ts:323:7) {
  generatedMessage: true,
  code: 'ERR_ASSERTION',
  actual: false,
  expected: true,
  operator: '=='
}