Enable eth_call state override

[nbaztec]

What does it do?

enabled eth_call state override as supported by geth

Fixes #1860

✔️ eth_call now supports an optional third parameter that can be used to set state overrides for specific addresses (useful for mocking purposes). The object is a key-value structure where each key identifies the address to override, while the value is a mapping of different override-able parameters.

provider.send("eth_call", "latest", {
    "0x123...": {
        balance: "0xff",
        nonce: "0x01",
        code: "0x.......",
        state: {
            "0xabc...": "0x...",
        },
        stateDiff: {
            "0xdef...": "0x...",
        },
    }   
});

The fields are:

• balance - sets the balance for the address.
• nonce - sets the nonce for the address.
• code - sets the EVM bytecode for the address.
• state - fully sets the storage for the address as provided by the key-value pairs.
• stateDiff - selectively sets the storage for the address as provided by the key-value pairs.

See tests for examples.

What important points reviewers should know?

Is there something left for follow-up PRs?

What alternative implementations were considered?

Are there relevant PRs or issues in other repositories (Substrate, Polkadot, Frontier, Cumulus)?

What value does it bring to the blockchain users?

[tgmichel]

Added a typo comment otherwise looks good, great work!!