Differentiate batch errors.

[nlordell]

Currently batch errors are just treated as web3::Error::Transport errors. It would be beneficial for calling code if ExecutionError had a separate error variant for when the full batch call fails (as opposed to an inner call).

[SWASTIC-7]

@nlordell can i take this up?

[nlordell]

I am no longer working on the project, so you will have to ask an active contributor.

[squadgazzz]

This project is no longer actively maintained and will likely be deprecated.