Use the MedusaBackup objects host map for restore mappings

[adejanovski]

We still read the host map/topology info from the backup bucket although it is stored in the MedusaBackup objects themselves.
It would be good to simplify our codebase and avoid unnecessary network calls by using the MedusaBackup status to read the host map from the backup cluster and use it to compute the restore mapping.

Definition of Done

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1. Restore mapping is done by reading the MedusaBackup object status instead of invoking medusa through the GRPC server