Make it work on Openshift

[roivaz]

This PR makes the kuadrant setup in this repo work also for Openshift. The idea is that through the use of labels in argocd clusters, certain applications or overlays are applied to make exactly the same set of manifests work for both k8s and Openshift.
There are several items that still require some work:

• I haven't been able to make this work on openshift when argocd is installed through openshift-gitops. It seems that openshift-gitops applies several restrictions that make the applicationsets not work as expected. I ended up just using argocd-operator from the community catalog, which worked just fine. We'll have to revisit what's exactly the problem with openshift-gitops and how to fix it, then document it.
• Right now the observability stack is only installed on k8s. We need to add the Openshift overly, which I supose is significantly different.
• The namespace where applications and applicationsets are installed is hardcoded to be argocd. This could be made configurable somehow, but didn't think it's a priority right now.

Other things worth mentioning:

• the argocd instance needs to be cluster scoped, a namespaced scoped argocd instance won't be able to install crds in the cluster. The argocd instance also needs the kustomizeBuildOptions: '--enable-helm' option set.
• ossm3 is installed when in Openshift, community sail-operator when k8s
• the redis helm chart is suposed to automatically detect openshift and apply the appropriate securityContext, but this was not working for me and I had to force it.

I tried this in a Hypershift cluster, would be nice if you could test it in other clusters as well.