EIP-7002: Implement Validator Exit Contract system call

[lucassaldanha]

Our experimental implementation of EIP-7002 is doing some contract storage manipulation to execute the same logic as the system call implemented in the contract.

However, contract storage manipulation is not the best way of implementing this. The smart contract has all the logic to handle the system call. All we need to do is implement the mechanism to perform "send a tx" from the system account. I believe we do not have this logic in Besu at the moment, the closest thing I can think of is how we use a fake transaction in the TransactionSimulator, but we would need a way of ensuring that changes in contract storage are persisted.

System call specification: https://eips.ethereum.org/EIPS/eip-7002#system-call