Add geth as an EL type

# 🎯 Problem to be solved

We want to have no single point of failure in a 7 node cluster. 2 EL options aren't enough. 

We should add go-ethereum (geth) to `compose-el.yml`

# 🧪 Tests

- [ ] Works in local docker-compose
- [ ] Has a attested on a testnet at least once

