Use Giant Swarm image repository for official Kubernetes images

[AndiDog]

What this PR does / why we need it

Towards giantswarm/roadmap#1722.

Official Kubernetes images were previously still pulled from upstream repos such as k8s.gcr.io (deprecated) and registry.k8s.io. Private clusters may not want to open access to them, and in general we use our own image hosting (e.g. Docker Hub, Quay) to remain reliable. The switch to Docker Hub requires that clusters have working Docker Hub credentials, or else will soon run into their drastic rate limits for anonymous image pulls.

As prerequisite, I had changed retagger to mirror the needed images (giantswarm/retagger#780). Mind kubernetes/kubeadm#2603 which can make the coredns image mirroring unnecessary in the future.

I successfully tested on golem whether the node rollout works using the new imageRepository value.

Checklist

• Update changelog in CHANGELOG.md.

Trigger e2e tests

/test create
/test upgrade

[AndiDog]

/test create
/test upgrade

Tekton pipeline didn't finish because of the merge commit that came later.

[tityosbot]

@AndiDog: The following tests failed, say /retest to rerun all failed tests:

Test name	Commit	Details	Rerun command
create	1fe0d29	link	/test create
upgrade	1fe0d29	link	/test upgrade

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository. I understand the commands that are listed here.

[tityosbot]

@AndiDog: The following tests failed, say /retest to rerun all failed tests:

Test name	Commit	Details	Rerun command
create	1fe0d29	link	/test create
upgrade	1fe0d29	link	/test upgrade

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository. I understand the commands that are listed here.