Implement WAF for ALB

[lorenyu]

Design notes

• Put WAF resources in the network layer so that WAF rules can be shared across all apps in a network

References

• https://docs.bridgecrew.io/docs/ensure-public-facing-alb-are-protected-by-waf
• https://docs.aws.amazon.com/waf/latest/APIReference/Welcome.html
• https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/wafv2_ip_set

[coilysiren]

Here's +1 example of the configuration needed to deploy a WAF: https://github.com/HHS/simpler-grants-gov/blob/c0edd3bc360f8b855ea3dee5bef08f22b1078597/infra/modules/service/waf.tf, via @aplybeah