Add more Kubernetes metrics to monitoring

As part of the readiness review and an evaluation of features we should be dogfooding we started to look at Kubernetes metrics and decided that it would be nice to have some additional panels to make this feature more useful for GitLab.com.

Here are the feature gaps we would like to address:

• Currently the infra team is using a set of Kubernetes dashboards using the kubernetes mixin, this provides a large set of panels.
• To use the built-in metrics we must be using label and naming conventions that I do not think work if we are bringing our own Kubernetes cluster and using a custom namespace https://docs.gitlab.com/ee/user/project/integrations/prometheus_library/kubernetes.html