Add State Override Support for eth_call

[Jouzo]

Summary

Extend eth_call RPC to include a state_overrides parameter for more flexible contract testing.

Rationale

This allows end users to specify a temporary state against which testing their contract deployment or interaction. This override should be temporary and should not affect the actual state of the blockchain. This ensures that developers can run these simulations without unintentionally altering the state of the blockchain.
This helps developer with smart contract debugging and analysis.
It can potentially reduce the amount of code deployed on-chain. Code that simply returns internal state or does pre-defined validations can be kept off chain and fed to the node on-demand.

Design

Additional state override struct :

struct StateOverride {
	pub balance: Option<U256>, 
	pub nonce: Option<U256>,
	pub code: Option<Bytes>, // code of the contract, if any
	pub state: Option<BTreeMap<H256, H256>>, // state of the contract
	pub state_diff: Option<BTreeMap<H256, H256>>, // the difference in state from the original
}

BTreeMap<H160, StateOverride>

RPC

eth_call example :

eth_call { from: "0xd9c9cd5f6779558b6e0ed4e6acf6b1947e7fa1f3", to: <contract_address>, input: <data> } "latest"
{
  "0xd9c9cd5f6779558b6e0ed4e6acf6b1947e7fa1f3": {
    "balance": "0xde0b6b3a7640000"
  }
}

The balance of the from address is set to "0xde0b6b3a7640000" for the context of this call

---

Ref : https://geth.ethereum.org/docs/interacting-with-geth/rpc/ns-eth

[Jouzo]

Can add an Optional to EVMBackend from_root method once
#2611 is in. Should be a pretty straightforward impl