Track new events on subgraph used by MACI scripts

[pettinarip]

Currently the genProofs script from MACI is doing:

const signUpLogs = await provider.getLogs({
    ...maciContract.filters.SignUp(),
    fromBlock: 0,
})

const publishMessageLogs = await provider.getLogs({
    ...maciContract.filters.PublishMessage(),
    fromBlock: 0,
})

Let's track those events in the subgraph in order to query them from there instead of using getLogs (that is expensive and with Arbitrum is not working).

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Error logs using an alchemy rpc:

Error: Requested block range for eth_getLogs is greater than the limit of 2000 blocks. Please reduce range and retry.

Error logs using the offcial testnet arbitrum rpc:

Error: timeout