Add CI job to validate Prepare-Node.ps1

[antoninbas]

Prepare-Node.ps1 is meant to be run once when preparing a Windows Node for K8s / Antrea installation.
Since we provide our own customized script (instead of relying on https://github.com/kubernetes-sigs/sig-windows-tools/blob/master/hostprocess/PrepareNode.ps1) and we point users to it in our Windows installation document, we should make sure that the script works correctly every time we cut a new Antrea release. This script is not currently exercised in our Windows CI jobs, as it is only run once to prepare worker Nodes when setting up the cluster (test clusters persist across CI jobs), and it is not run by the CI jobs themselves.
It would be a good idea to have an on-demand Jenkins job to validate the script, that we can trigger when we prepare a new release.

[antoninbas]

The job may be able to catch issues in Prepare-AntreaAgent.ps1 as well, such as #5852

[github-actions]

This issue is stale because it has been open 90 days with no activity. Remove stale label or comment, or this will be closed in 90 days

[github-actions]

This issue is stale because it has been open 90 days with no activity. Remove stale label or comment, or this will be closed in 90 days