Cleanup GenerateCIArtifactsInjectedTemplateForDebian

[sbueringer]

What steps did you take and what happened:
I duplicated the GenerateCIArtifactsInjectedTemplateForDebian func of cluster-api because the upstream func doesn't work in our case (yet)

It has the following issues:

1. they are using gsutil instead of curl. Thus they install google cloud sdk first which adds ~3-5 minutes to to node startup in our environment (probably in all environments)
2. they are also pulling the "kube-apiserver" "kube-controller-manager" "kube-scheduler" for worker nodes, which is not necessary and also adds time to the test
   3/ when we use the upstream method to patch our KubeadmControlPlane and KubeadmConfigTemplate to add the /usr/local/bin/ci-artifacts.shscript we will lose the/etc/kubernetes/cloud.confand/etc/certs/cacertfiles because the wholefiles` array is overwritten. This is a limitation of kustomize, but I assume with the fixes merged to kustomize a week ago we are able to improve this (Strategic merge support for CRDs kustomize#2825) (although it's not completely trivial)

Goal of this issue is to I to improve all those things in the cluster-api util func GenerateCIArtifactsInjectedTemplateForDebian I currently copied into tmp_template.go and then drop the copy in our repo.

Anything else you would like to add:
xref: #782 (comment)

[sbueringer]

/assign