Rename go-web3 to ethgo

[ferranbt]

This is a tracking issue to manage any problems during the renaming of the library from go-web3 to ethgo.

Initially, the name go-web3 was meant to be a reference to web3.js, one of the official javascript libraries for Ethereum. However, as time passed, the name web3 has become a generic name on the industry for many blockchain related applications. This might be confusing for developers since this library is only meant to be used for Ethereum compatible blockchains.

In that regard, I think the new name makes a much more clear statement of what the library does.