Multi-stage cluster addons: Docker cluster stacks with support of multi-stage cluster addon

[janiskemper]

/kind feature

Describe the solution you'd like
I want to have Docker cluster stacks with multiple K8s versions that we can use to test and showcase the multi-stage cluster addon feature. These cluster stacks should contain valid cluster addons and use the pre and post conditions to wait for the different stages.

Currently, we have cluster stacks with cluster addons that are good for testing, but that don't really make a lot of sense from DevOps perspective and are therefore not good for showcasing the feature to others.

For now, the cluster stacks can be put in the test directory in this repo, but we can think to also put them in the official cluster-stacks repo of SCS later.

Minimum clusters tacks that we need:

1. One cluster stack with a certain Kubernetes version and respective node images
2. One cluster stack that updates cluster addons compared to the first one
3. One cluster stack that updates cluster addons as well as Kubernetes version compared to the second.

We need those three in order to test both flows, one without upgrade of K8s version and one with.