Etheno needs to be redesigned, removing features are unused or broken

[ggrieco-tob]

Right now, Etheno is an important part of end-to-end testing using Echidna, however most of the features are not related to that and tend to break the rest of the tool. Right now, we need to remove all the code that is barely used, including:

• Manticore integration (which is breaking is producing some issues since it tends to be broken)
• EVM differential testing: I don't think this was used beyond the initial experiments we did.
• Echidna fuzzing: this is unused and confuses the users since it looks related with end-to-end testing, but it is not.

When we have a more reduced codebase, we can start with other improvements.

[anishnaik]

Parity integration will also be removed since it is no longer supported and is now called openEthereum