[Feature] Connect to private clusters with Cloud Shell in a VNet

Connecting to private clusters is difficult, often required custom complex setups. We want to make it easier by using Cloud Shell in a VNet to connect to private AKS clusters. [Cloud Shell in a VNet](https://learn.microsoft.com/en-us/azure/cloud-shell/vnet/overview) is a GA feature. This work item is for enabling easy setup and connectivity for AKS users. While Bastion is good for persistent access and managing many clusters, Cloud Shell is good for cost-effective ad-hoc access.

An easy setup button in Portal is currently in Public Preview. [Learn more](https://review.learn.microsoft.com/en-us/azure/aks/private-clusters#options-for-connecting-to-the-private-cluster).

Upcoming work includes support for AKS Automatic clusters and clusters with NRG lockdown.