Set a unique valid default name for nodepool when spec.name in AzureManagedMachinePool is not specified

[tapojit047]

/kind bug

What steps did you take and what happened:

• Create an AKS Cluster using CAPZ
• Create a new MachinePool without specifying optional field spec.name in AzureManagedMachinePool
• Got the error below:

 message: 'agentpools failed to create or update. err: failed to create resource
      tapo-test/multiple-zone-dedicated (service: agentpools): failed to begin operation:
      Code="InvalidParameter" Message="The value of parameter agentPoolProfile.name
      is invalid. Please see https://aka.ms/aks-naming-rules for more details." Target="agentPoolProfile.name"'
    reason: Failed

What did you expect to happen:
If I do not mention the spec.name field in AzureManagedMachinePool, it should be able to generate a default unique spec.name such that the MachinePool is created.

Anything else you would like to add:

• The error is raised here
• It is raised because of this naming restriction of nodepool in AKS: Limitations

Environment:

• cluster-api-provider-azure version: v1.10.3
• Kubernetes version: (use kubectl version): v1.27.3