This implements pushing to and pulling from Kubernetes cluster discovery
registry which is simply using extra Talos annotations on the Node
resources.
Note: cluster discovery is still disabled by default.
This means that each Talos node is going to push data from its own local
`Affiliate` structure to the `Node` resource, and also watches the other
`Node`s to scrape data to build `Affiliate`s from each other cluster
member.
Further down the pipeline, `Affiliate` is converted to a cluster
`Member` which is an easy way to see the cluster membership.
In its current form, `talosctl get members` is mostly equivalent to
`kubectl get nodes`, but as we add more registries, it will become more
powerful.
Signed-off-by: Andrey Smirnov <andrey.smirnov@talos-systems.com>
