retina-shell support for Windows

[wedaly]

Is your feature request related to a problem? Please describe.
Add support to retina-shell for Windows nodes.

Describe the solution you'd like

• Create and publish retina-shell image that can run on Windows.
• Update retina-shell CLI to run this image on Windows nodes.

Describe alternatives you've considered
N/A

Additional context

• Windows currently blocked by this validation

  retina/shell/validation.go

  Lines 14 to 25 in 4ce4881

  	func validateOperatingSystemSupportedForNode(ctx context.Context, clientset *kubernetes.Clientset, nodeName string) error {
  	node, err := clientset.CoreV1().
  	Nodes().
  	Get(ctx, nodeName, metav1.GetOptions{})
  	if err != nil {
  	return fmt.Errorf("error retrieving node %s: %w", nodeName, err)
  	}
  	osLabel := node.Labels["kubernetes.io/os"]
  	if osLabel != "linux" { // Only Linux supported for now.
  	return errUnsupportedOperatingSystem
  	}

• Can use host process containers, similar to what Patrick did for node shell Add support for Windows nodes kvaps/kubectl-node-shell#45
• Windows base images are large, so probably want to keep it separate from the Linux retina-shell image rather than using multi-arch.
• I'm not sure all the retina-shell CLI params make sense for Windows, so might need to adjust those (it's marked "experimental" so breaking changes should be okay)