Add cluster hardening tests (#759)

* Add first tests for cluster hardening standard

Signed-off-by: michal.gubricky <michal.gubricky@dnation.cloud>

* Add test for Pod security admission controller

Signed-off-by: michal.gubricky <michal.gubricky@dnation.cloud>

* Add test for authorization methods

Signed-off-by: michal.gubricky <michal.gubricky@dnation.cloud>

* Add test for authentication methods

Signed-off-by: michal.gubricky <michal.gubricky@dnation.cloud>

* Add test if communication with etcd is secured via TLS

Signed-off-by: michal.gubricky <michal.gubricky@dnation.cloud>

* Add test whether the etcd is isolated from k8s cluster

Signed-off-by: michal.gubricky <michal.gubricky@dnation.cloud>

* Rebase after current sonobuoy golang framework was restructured

Signed-off-by: michal.gubricky <michal.gubricky@dnation.cloud>

* Adjust test for etcd tls communication

Signed-off-by: michal.gubricky <michal.gubricky@dnation.cloud>

* Adjust test which checks if kubelet readonly port is disabled

Signed-off-by: michal.gubricky <michal.gubricky@dnation.cloud>

* Remove unused functions

Signed-off-by: michal.gubricky <michal.gubricky@dnation.cloud>

* Remove development artifact

Signed-off-by: michal.gubricky <michal.gubricky@dnation.cloud>

* Restructure the code to make it a bit more clearly

Signed-off-by: michal.gubricky <michal.gubricky@dnation.cloud>

* Update kind config

Signed-off-by: michal.gubricky <michal.gubricky@dnation.cloud>

* Remove kubeadmConfigPatches section in kind_config.yaml

Signed-off-by: michal.gubricky <michal.gubricky@dnation.cloud>

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Signed-off-by: michal.gubricky <michal.gubricky@dnation.cloud>
Co-authored-by: cah-patrickthiem <140701884+cah-patrickthiem@users.noreply.github.com>

Author: michal-gubricky