Making ObjectMeta in CloudStackMachineTemplateResource nullable

[maxdrib]

Issue #, if available:

Description of changes:
We have a usecase in EKS-A where we serialize a Go object, then apply it to the cluster. When we try to do this with a CloudStackMachineTemplate, the resulting object looks like

apiVersion: infrastructure.cluster.x-k8s.io/v1beta2
kind: CloudStackMachineTemplate
metadata:
  creationTimestamp: null
  name: drib-upgrade-control-plane-template-1665592860423
  namespace: eksa-system
spec:
  template:
    metadata:
      creationTimestamp: null
    spec:
      diskOffering:
        customSizeInGB: 0
        device: ""
        filesystem: ""
        label: ""
        mountPath: ""
      offering:
        name: Large Instance
      sshKey: ""
      template:
        name: rhel-8-kube-v1.21.5-new

and when it gets applied, we observe a validation error from the kube-api server:

unknown object type "nil" in CloudStackMachineTemplate.spec.template.metadata.creationTimestamp; if you choose to ignore these errors, turn validation off with --validate=false

Given that this objectmeta is unused in the CAPC codebase, instead of removing it, I think we should make it nullable for backwards compatibility.

Testing performed:
Generated new CAPC infrastructure-components and created cluster with them. Applied the serialized CloudStackMachineTemplate above and it succeeded without validation errors.

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This pull-request has been approved by: maxdrib, rejoshed

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