Prow: allow deployment of kubernetes-external-secrets without roles/container.admin

[spiffxp]

Should be able to CRUD kubernetes resources without CRUD rights for the cluster

Some work has already been done toward this, to link in later

[spiffxp]

/area prow
/area cluster-infra
/sig testing
/wg k8s-infra
/priority important-longterm

[spiffxp]

#2190 setup a custom container.deployer role

But that apparently still isn't sufficient: #2190 (comment)

[spiffxp]

/milestone v1.23

[spiffxp]

It seems like creating RBAC-related resources is the sticking point here. I suspect container.admin is by default given a Kubernetes role that allows it to do so, but custom roles maybe not so much?

[spiffxp]

/milestone v1.22
If I can't figure out what's preventing the custom role I'm going to add back container.admin for now to unblock auto-deploys