This breaks up our release monolith. (#2162)
This breaks up our release monolith. (#2162)

The release now publishes the following units in addition to the "bundles":
 * build.yaml (just build)
 * serving.yaml (just serving)
 * monitoring-lean.yaml (the "lite" portions of monitoring)
 * monitoring.yaml (all monitoring stuff)
 * istio-lean.yaml (just istio ingress functionality)
 * istio.yaml (the full service mesh)

This preserves the 3 existing "bundles" that we produce, but constructs them in terms of the above.
knative/serving,knative/serving