Upgrade sigs.k8s.io/controller-runtime to v0.9, k8s.io/* to v0.21

[rfranzke]

How to categorize this issue?

/area open-source
/kind enhancement
/priority 3

What would you like to be added:
sigs.k8s.io/controller-runtime has released v0.9.0, see https://github.com/kubernetes-sigs/controller-runtime/releases/tag/v0.9.0. It vendors k8s.io/* at v0.21, so we can go ahead and update our dependencies as well.

[rfranzke]

/cc @timebertt - would you be interested in taking this again?

[timebertt]

I can already sense some trouble, but I'll do it 😉
/assign

[rfranzke]

Great, thanks! Let's hope for the best... :)

[timebertt]

/in-progress

[timebertt]

Ok, upgrade should not bring many difficulties.
Nevertheless, here is a list of a few (breaking) changes upstream to look out for when vendoring g/g, k/* and c-r in any of our repos (e.g. extensions):

Most important changes in k-s/c-r@v0.9 to look out for (see the release notes for complete list and more details)

• ⚠️ breaking / most notable changes:
  • Envtest Refactor & Support for 1.20+ Clusters (#1486) => mainly adds authn and authz to envtest; should not be breaking for other repos, if they don't mess with the given rest config or similar things
  • Envtest Setup Tool (#1488) => adapted our hack/setup-envtest.sh script as well, might need some adaption in make install-requirements if other repos also fetch the envtest binaries
  • Update Kubernetes v1.21 dependencies and use Go 1.16 (#1389) => obvious one, but still mentioning it here
  • Allow setting NewClientFunc w/o implementing an interface (#1409)
  • Fakeclient: Handle Finalizers (#869)
  • client.*MergeFrom* now take client.Object instead of runtime.Object (#1395)
• ℹ️ other changes / good to know / for information only:
  • Structured args in Testing (#1541) -- the use of templated args (Environment.KubeAPIServerFlags) is now deprecated -- use GetAPIServer().Configure() instead => no change needed, if you aren't doing any custom configuration for the envtest control plane components
  • Add SelectorsByObject option to cache (#1435) => allows to have specialized / filtered watches in controller-runtime
  • Add ClientWithWatch for use in CLIs (#1460)
  • Honor LeaderElectionReleaseOnCancel (#1523)