Feature Request: Option to disable Etherscan downloads with onchain fuzzing

[rappie]

Describe the desired feature

During the development of a fuzzing campaign I am rarely interested in coverage. It takes an extra CTRL+C to close Echidna, and it is a waste of unused resources 🙂

[ggrieco-tob]

This seems fair, I think Etherscan should be used only if RPC is enabled.

[rappie]

Actually, I would like the option to fully disable it. In practice I would have it disabled by default in all cases and only enable it when I'm actively investing coverage or doing production runs.

[ggrieco-tob]

If you do not specify a corpus directory, it will not write any coverage.