General availability: Ultra disks support on AKS

[Azure ultra disks](https://docs.microsoft.com/en-us/azure/virtual-machines/disks-enable-ultra-ssd) offer high throughput, high IOPS, and consistent low latency disk storage for your stateful applications. One major benefit of ultra disks is the ability to dynamically change the performance of the SSD along with your workloads without the need to restart your agent nodes. Ultra disks are suited for data-intensive workloads. * Azure Kubernetes Service (AKS) * Features * [ Azure Kubernetes Service (AKS)](https://azure.microsoft.com/en-gb/products/kubernetes-service/)