Allow calculating additional ARO worker nodes in Azure Pricing Calculator

The Azure Pricing Calculator for ARO always requires 3 master nodes and a minimum of 3 worker nodes. While this is fine for new systems, it is severely limiting when trying to estimate costs for workloads that are added to *existing OpenShift clusters* and therefore just require additional worker nodes.

I'm therefore asking to please make the **master nodes optional** and allow us to specify a **minimum of 1 worker nodes**.

You could show a warning that a minimum of 3 is required for new clusters, or make 3 the minimum when master nodes are selected.

This would also make it much easier to calculate prices when using multiple MachineSets. You could then e.g. add one full ARO and another one with just worker nodes.