Kustomize

What does this MR do?

Adds kustomize binary (https://kubectl.docs.kubernetes.io/references/kustomize/ and https://github.com/kubernetes-sigs/kustomize)

Helmfile has support for it (https://github.com/roboll/helmfile/blob/master/docs/advanced-features.md#deploy-kustomizations-with-helmfile) but it needs the binary to use it.

Manual QA

docker run -it --rm registry.gitlab.com/deployable-nl/gitlab/cluster-applications/kustomize:latest kustomize version
{Version:kustomize/v4.5.4 GitCommit:cf3a452ddd6f83945d39d582243b8592ec627ae3 BuildDate:2022-03-28T23:12:45Z GoOs:linux GoArch:amd64}