tape: store datastore name in tape archives and media catalog

So that we can store multiple datastores on a single media set.
Deduplication is now per datastore (not per media set).

src/api2/types/tape/media.rs

@@ -144,6 +144,8 @@ pub struct MediaContentEntry {
     pub seq_nr: u64,
     /// Media Pool
     pub pool: String,
+    /// Datastore Name
+    pub store: String,
     /// Backup snapshot
     pub snapshot: String,
     /// Snapshot creation time (epoch)