[RFE] Implement `ssh` command

## Current situation

`kubectl aks` doesn't provide a way to ssh into the nodes (VMSS instances) of an AKS cluster.

## Ideal future situation

Investigate if how we can implement something like this:

```
$ kubectl aks shh --node aks-agentpool-12345678-vmss000000
# shell in the node
```

Of course, the idea solution is to not depend on the Kubernetes control plane but use the Azure SDK to be able to provide this functionality even when the Kubernetes control plane is not working properly, e.g. the API server is down. Note: Check if this kind of functionality is also available for VMSS: https://learn.microsoft.com/en-us/cli/azure/ssh?view=azure-cli-latest#az-ssh-vm

However, if it is not possible, we still have the option of using [`kubectl-node-shell`](https://github.com/kvaps/kubectl-node-shell) and provide this functionality only if Kubernetes is working properly.

Start by comparing Azure VMSS SSH support with the kubectl-node-shell approach described in the issue. Determine whether the command can work when the Kubernetes control plane is unavailable, then define the supported `kubectl aks ssh --node` behavior and verify it against both possible implementation paths.

Written by the indexing model from the issue text.