[etcdsnapshot&restore] Create a single automatic snapshot per cluster

[Danil-Grigorev]

To reduce number of created snapshots per cluster, we can encapsulate multiple automatic snapshots for a cluster in a single resource within the resource status, instead of creating a separate one per each automatic snapshot.

This should address scalability concerns and provide a better UX working with automatic RKE2 snapshots.

Context from proposal:

Just an idea here: potentially this number can be decreased from N*M to just N where N is the number of clusters and M is the ~number of preserved snapshot per each cluster, if the automatic snapshot will be treated as a “full cluster” state. Instead of creating a resource per each snapshot resource, there will be one snapshot resource synced to the management cluster. Automation will take care of updating name of the node and file/S3 reference, where the snapshot has taken place inside this single resource, and potentially specifying alternative up-to-date snapshots in a status, which can be used as a source for restore.