KubeCarrier Addon for KKP

[rastislavs]

The aim of this topic is to provide seamless installation of KubeCarrier in KKP.

An POC of a KKP addon was already done as part of https://github.com/kubermatic/kubecarrier/pull/554

This POC uncovered a few issues:

• Since the plugin contains multiple CRDs and their instantiations at the same time, it takes several attempts in reconciliation loop until it is successfully applied. That results into several warnings in the cluster event log in the KKP UI.
• Since KubeCarrier requires cert-manager to run, cert-manager has to be installed prior to KubeCarrier. If they are both installed at once as part of the same plugin, it takes long time (several minutes) until everything converges and KubeCarrier is ready. Sometimes, KubeCarrier does not even start at all.