Autogenerate Ethereum private keys for Codex nodes

[veaceslavdoina]

It might be useful to autogenerate Ethereum private keys, especially for internal/in-cluster/testing purposes.

And we should add an important note about that approach:

Warning

After nodes were deployed, we should manually create backups of the private keys to redeploy them in case of failure or at least get access to move the tokens in case of need.