[Azure] Add Terragrunt configuration for different cluster deployment types

[baserrato]

Instead of deployments to hypothetical test and prod environments, Terragrunt should instead reflect the following deployment types in Azure:

• [x] Public AKS cluster with public Kubernetes API server endpoint and load balancer
• [x] Semi-private AKS cluster with private server endpoint but internet facing load balancer
• [x] Private AKS cluster with private server endpoint and user-defined route to Azure Firewall
• [ ] AKS cluster with secondary node pool consisting of preemptible VMs
• [ ] AKS cluster using secondary node pool with virtual nodes backed by ACI