feat(eth_call): fix serializion to include default block to latest

[0xfourzerofour]

Motivation

In an eth_call the block parameter is always required. In the current serialization logic, it does not add a block if the state_overrides is None and the block is None.

This results in a node returning an invalid parameter error.

Solution

I have updated the code to always set the block as the second argument, if it is None it will use the default latest value. The third argument will only be added if state_overrides is Some.

PR Checklist

• [y] Added Tests
• [y] Added Documentation
• [n] Breaking changes

[DaniPopes]

the block parameter is not required as per the RPC spec, so it's on the node to accept a missing block parameter
we don't serialize it as some nodes also don't support it at all

[mattsse]

this param is optional,
I think we don't need to set it and leave this up to the node to pick the default

[0xfourzerofour]

damn, no worries I shall fix on my client side