Add support for BYO VMSS for AzureASOManagedCluster

[arsdragonfly]

/kind feature

Currently BYO VMSS is only supported for AzureManagedCluster or AzureCluster, but not AzureASOManagedCluster.

E0207 00:38:34.638919       1 controller.go:324] "Reconciler error" err="failed to create cluster scope for cluster default/zheyurg3-zheyuslinky3: unsupported infrastructure type \"AzureASOManagedCluster\", should be AzureCluster or AzureManagedCluster" controller="azuremachinepool" controllerGroup="infrastructure.cluster.x-k8s.io" controllerKind="AzureMachinePool" AzureMachinePool="default/zheyurg3-zheyuslinky3-vmss" namespace="default" name="zheyurg3-zheyuslinky3-vmss" reconcileID="cb829e8a-88fb-48cf-8049-626fc25ed917"

Per discussion with @willie-yao on Slack, this could supposedly be done by extending AzureASOMachinePool to support self-managed VMSS.

[nawazkh]

Putting this on a back burner for now to address AKS + BYO nodes issue. Ref: https://kubernetes.slack.com/archives/CEX9HENG7/p1739286535640709

[nawazkh]

Sorry, I won't be able to get to it as of now, un-assigning myself
/unassign