upgrade state root

[krlosMata]

Summary

circuit to upgrade the state root of the rollup with a decentralized mechanism. this circuit will be linked to its smart contract function to assure fully and correct state root upgrade

Rationale

All accounts must be updated to their new account fields. Basically, two new fields would be added in each leaf: exitBalance = 0 and accumulatedHash = 0 Circuit should do the following:

• take old root
• proof existence for each account in the old root
• process new root with new fields for each account

Notes

• Circuit parameter would be nLevels and nAccounts
• Optimize nAccounts in order to perform less smart contract calls to upgrade all accounts

[krlosMata]

implemented in https://github.com/hermeznetwork/circuits/pull/47