Improve distribution of machines

[mcbenjemaa]

Describe the solution you'd like
[A clear and concise description of what you want to happen.]

Currently, we distribute the nodes via ProxmoxCluster.spec.allowedNodes but this field won't help us to distribute the machines into different Proxmox hardware nodes.
We need to extend the way of placing machines so we could have a Node pool per zone or something.

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

I have a proposal that I have discussed with our colleagues.

Proposal

Add a field in ProxmoxMachine and ProxmoxMachineTemplatespec.allowedNodes.
this field will override the way of distributing the nodes for this certain Machine, MachineDeployment.

spec:
  allowedNodes:
  - pve1
  - pve2
  - pve3

If ProxmoxMachine sets the allowedNodes it will take precedence over the ProxmoxCluster allowedNodes.
If no allowedNodes defined in the Machine, it will use the Cluster by default.

Environment:

• Cluster-api-provider-proxmox version:
• Kubernetes version: (use kubectl version):
• OS (e.g. from /etc/os-release):

[wikkyk]

Makes sense to me. The more granular ProxmoxMachine.allowNodes overriding the more global ProxmoxCluster.allowedNodes is exactly what you'd expect.