Add CopyVolumeDataAll and PrepareDataAll functions

[laurentiusoica]

For datastores with multiple replicas, having the "All" alternatives for CopyVolumeData and PrepareData is useful in order to:

• avoid phase duplication for each of the replicas
• address use cases where the number of replicas for the datastore can change in Day 2. Without the "All" alternative, a blueprint update is required with each scale
• have a single blueprint regardless of the setup of the datastore in various environments

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[mlavi]

As discussed in Kanister Slack, will defer until additional Kopia work lands in Kanister to address this request.

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