[feature] Support scheduling resources with CRP without rollout

[vasudev-bongale]

At LinkedIn we use ClusterResourcePlacement custom resource as the source of truth for the existence of a namespace in member clusters. Other services rely on this information to discover clusters to read/write objects into these namespaces directly into the member clusters.
However there are namespaces that exist both in Hub and the member clusters. For e.g: kube-system. If we were to create a CRP for these namespaces, the objects in the Hub will overwrite the objects in the member cluster.

The CRP currently allows defining a rollout strategy. A way to specify opting out of the rollout but allow scheduling in CRP will serve the ask of having placement information but not propagating the resources.

[zhiying-lin]

@vasudev-bongale could you please describe However there are namespaces that exist both in Hub and the member clusters. For e.g: kube-system. If we were to create a CRP for these namespaces, the objects in the Hub will overwrite the objects in the member cluster. a little bit?

If you don't want the hub cluster overwrites the objects in these namespaces, why not creating a CRP to not select these namespaces? or you can configure the fleet to skip these namespaces by using skipped-propagating-namespaces.

In addition, by default, any reserved namespace ("kube-" or "fleet-") will be skipped. code link