Correctly calculate disk usage for frozen data tier telemetry (#86580) (#86749)

The telemetry for data tiers was using the size in bytes, however, for
the frozen tier using searchable snapshots, this was the disk usage
rather than the size of the actual data.

This commit changes the telemetry to use `total_data_set_size` as
introduced in #70625 so that the telemetry is correct.

Resolves #86055

Author: dakrone

docs/changelog/86580.yaml

@@ -0,0 +1,6 @@
+pr: 86580
+summary: Correctly calculate disk usage for frozen data tier telemetry
+area: Stats
+type: bug
+issues:
+ - 86055

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/DataTiersFeatureSet.java

@@ -198,7 +198,7 @@ private static void aggregateDataTierShardStats(NodeStats nodeStats, Index index
         final List<IndexShardStats> allShardStats = nodeStats.getIndices().getShardStats(index);
         if (allShardStats != null) {
             for (IndexShardStats shardStat : allShardStats) {
-                accumulator.totalByteCount += shardStat.getTotal().getStore().getSizeInBytes();
+                accumulator.totalByteCount += shardStat.getTotal().getStore().totalDataSetSizeInBytes();
                 accumulator.docCount += shardStat.getTotal().getDocs().getCount();
 
                 // Accumulate stats about started shards
@@ -210,7 +210,7 @@ private static void aggregateDataTierShardStats(NodeStats nodeStats, Index index
                     if (primaryStoreStats != null) {
                         // if primaryStoreStats is null, it means there is no primary on the node in question
                         accumulator.primaryShardCount++;
-                        long primarySize = primaryStoreStats.getSizeInBytes();
+                        long primarySize = primaryStoreStats.totalDataSetSizeInBytes();
                         accumulator.primaryByteCount += primarySize;
                         accumulator.valueSketch.add(primarySize);
                     }

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/DataTiersFeatureSetTests.java

@@ -769,7 +769,7 @@ private List<NodeStats> buildNodeStats(ClusterState clusterState, long bytesPerS
     }
 
     private static ShardStats shardStat(long byteCount, long docCount, ShardRouting routing) {
-        StoreStats storeStats = new StoreStats(byteCount, 0L, 0L);
+        StoreStats storeStats = new StoreStats(randomNonNegativeLong(), byteCount, 0L);
         DocsStats docsStats = new DocsStats(docCount, 0L, byteCount);
 
         CommonStats commonStats = new CommonStats(CommonStatsFlags.ALL);