feature: Add support for hostnames where ips are required

[Davidson-Souza]

We have a couple of places where we need to pass IP addresses, like in --rpc-address, --electrum-address and the RPC addnode. It would be nice if we could use hostnames too. This is specially useful in the binding addresses because if you're using Docker Compose or another automated environment, you may not know the IP, that is dynamically assigned to the host and resolved using the service name.