Removing the only system nodepool from cluster via API does not show error

[valaparthvi]

Rancher: v2.9-0d8af1460cfc73c3bf4bafecc38f399ea5c187a3-head
Dashboard: release-2.9 65f0232
Operator Version: rancher-aks-operator:104.0.1+up1.9.0

Steps to reproduce:

1. Import a cluster with a single 'System' mode nodepool, and a user mode nodepool
2. Removing the 'System' mode nodepool via API

Result:
The update does not result in cluster to error out.
The UI shows error 'At least 1 system nodepool is required, but there is no error in the operator logs or cluster object.

For a provisioned cluster, the operator logs and cluster.Transitioning and cluster.TransitioningMessage both show appropriate error messages.

PR's:

• Prevent from removing last node pool with mode System #694

[cpinjani]

Validation passed on build: v2.10-head, aks-operator:v1.10.0-rc.2
Removing the only system nodepool from provisioned/imported cluster via API throws error