Allow state override on eth_estimateGas

[antonydenyer]

Rationale

Currently, you can not perform an eth_estimateGas on something that isn't in the 'correct' state as the evm will, correctly, return an error. For example, on an erc20 you may wish to send an approve followed by a transfer call. You can estimate gas for the approve but not the transfer.

Implementation

Add an additional parameter to the end of the request in the same way eth_call does.
Are you willing to implement this feature? Yes

[s1na]

Hi @antonydenyer. I think it makes sense to add these overrides, and probably the block overrides which have recently been added to eth_call as well.

You indicated you're willing to implement this feature. I'd personally welcome your contribution and can gladly review it.