test/monitoring uses some k8s deps that are not published upstream.
imports should be replaced by modules from github.com/openshift/kubernetes

That complicates the root go.mod and make deps bumps confusing.

The deps of test/monitoring are not expected to change frequently, since the code is in maintenance mode and the Kubernetes Version Skew Policy is relatively loose.

let's make test/monitoring a submodule with its own deps.