### Elasticsearch Version

8.1.2

### Installed Plugins

_No response_

### Java Version

_bundled_

### OS Version

ESS on Azure

### Problem Description

The `_xpack/usage` API reports the size of the data set per data tier. However, it uses the local disk size as the metric it reports on and this is 0 (zero) for partially mounted indices, hiding the size of the data set mounted on the frozen tier.

We should switch to using the `total_data_set_size` metric that was introduced when we added the frozen tier/partially mounted indices.

### Steps to Reproduce

Mount a partially mounted index on a dedicated frozen tier. Use the `_xpack/usage` API and see that no (or very little) data is reported on frozen tier.

### Logs (if relevant)

_No response_
x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/DataTiersUsageTransportActionTests.java
settingsBuilder.put(DataTier.TIER_PREFERENCE, dataTierPrefs[0]);
        }
        return IndexMetadata.builder(indexName).settings(settingsBuilder.build()).timestampRange(IndexLongFieldRange.UNKNOWN).build();
    }
    private static void routeTestShardToNodes(
        IndexMetadata index,
        int shard,
        IndexRoutingTable.Builder indexRoutingTableBuilder,
        DiscoveryNode... nodes
    ) {
        ShardId shardId = new ShardId(index.getIndex(), shard);
        IndexShardRoutingTable.Builder indexShardRoutingBuilder = new IndexShardRoutingTable.Builder(shardId);
        boolean primary = true;
        for (DiscoveryNode node : nodes) {
            indexShardRoutingBuilder.addShard(
                TestShardRouting.newShardRouting(shardId, node.getId(), null, primary, ShardRoutingState.STARTED)
            );
            primary = false;
        }
        indexRoutingTableBuilder.addIndexShard(indexShardRoutingBuilder.build());
    }
    private List<NodeStats> buildNodeStats(ClusterState clusterState, long bytesPerShard, long docsPerShard) {
        DiscoveryNodes nodes = clusterState.getNodes();
        RoutingNodes routingNodes = clusterState.getRoutingNodes();
        List<NodeStats> nodeStatsList = new ArrayList<>();
        for (DiscoveryNode node : nodes) {
            RoutingNode routingNode = routingNodes.node(node.getId());
            if (routingNode == null) {
                continue;
            }