Allow setting ResourceGroupName in AzureManagedControlPlaneTemplate

[MagnusRef]

⚠️ Cluster API Azure maintainers can ask to turn an issue-proposal into a CAEP when necessary. This is to be expected for large changes that impact multiple components, breaking changes, or new large features.

Goals

1. To be able to specify the resource group name of a AzureManagedControlPlaneTemplate just like in AzureManagedControlPlane.

Non-Goals/Future Work

1. N/A

User Story

As an operator I would like to be able name the resource group for the AKS cluster based on something else than the metadate.name of the cluster object.

Detailed Description

In my case I would like to name the resourcegroup the same as the metadata.controlPlaneRef.name of my cluster object, just like how it automatically picks up the controlplane name in self-managed kubeadm clusters in CAPZ.

This would from an operator point of view be done with JSON patching in the ClusterClass, if ResourceGroupName was exposed in the AzureManagedControlPlaneTemplate.

The reason for doing this is to not get into situations where multiple controlplanes gets deployed to the same resource group. This can happend if you have multiple management clusters, or loss of cluster state in a management cluster.

This Issue was made based on a this convosation on the cluster-api-azure slack channel:
https://kubernetes.slack.com/archives/CEX9HENG7/p1712320334762489

With information gathered from: #2684

Thank you!

Contract changes [optional]

Not sure

Data model changes [optional]

Not sure

/kind proposal

[willie-yao]

/assign

[willie-yao]

/kind feature