Feat: voice credit per tokens (ERC20 or ETH sent to an address)

[NicoSerranoP]

Description

We need a feature to give each voter a specific voice credit amount depending on how much ERC-20 tokens or ETH the user has send to an address. Related to https://github.com/privacy-scaling-explorations/maci/issues/1968

Steps:

1. Deploy the PerTokenVoiceCreditProxy contract
2. Send ERC20 tokens or ETH to the contract using registerVoiceCredits (this is happening outside any Poll or MACI function. Should it stay that way or should we integrate it into the joinPoll step?)
3. Vote into a specific poll. The contract will use getVoiceCredits to calculate how much credit a voter has

Related issue(s)

Close #1968

Confirmation

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