Round robin

The simplest load balancing policy available.
Takes all nodes in the cluster and uses them one after another.

For example if there are nodes A, B, C in the cluster, this policy will use A, B, C, A, B, ...


To use this policy in Session:

fn main() {
extern crate scylla;
use scylla::Session;
use std::error::Error;
async fn check_only_compiles() -> Result<(), Box<dyn Error>> {
use scylla::{Session, SessionBuilder};
use scylla::transport::load_balancing::RoundRobinPolicy;
use std::sync::Arc;

let session: Session = SessionBuilder::new()