Update docs on how to apply CAPA clusters

[Rotfuks]

Motivation

After the changes introduced by the release framework implementation there are some slight simplifications on how customers can apply changes to their clusters - for example by just using the cluster-aws chart without the need for any additional resource to be applied. We need to adapt the public docs accordingly.

Todo

• Adapt the public docs to match how to apply changes
• Adapt the operations cookbooks and any other intranet resource to the change

Outcome

• The alignment introduced with the release framework is not just implemented but also all documents around releasing and applying apps are matching to the reality.

[weseven]

Updated getting started docs with cluster template cli using releases giantswarm/docs#2268