Ensure cross zone load balancing is enabled for AWS ELB

AWS ELB has cross zone load balancing disabled which may cause it to be less resilient.

In AWS Console -

1. Sign in to AWS Console and open EC2 console.
2. On the navigation pane, under LOAD BALANCING, choose Load Balancers.
3. Select your load balancer.
4. On the Description tab, choose Change cross-zone load balancing setting.
5. On the Configure Cross-Zone Load Balancing page, select Enable.
6. Select Save.

In Terraform -

1. In the aws_elb resource, set the cross_zone_load_balancing field to true.

References:
https://docs.aws.amazon.com/elasticloadbalancing/latest/classic/enable-disable-crosszone-lb.html
https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/elb#cross_zone_load_balancing