### 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
assertThat(coldStats.primaryShardBytesMAD, is(0L)); 
    }
    public void testCalculateStatsMixedTiers() {
        
        int nodeId = 0;
        DiscoveryNodes.Builder discoBuilder = DiscoveryNodes.builder();
        DiscoveryNode leader = newNode(nodeId++, DiscoveryNodeRole.MASTER_ROLE);
        discoBuilder.add(leader);
        discoBuilder.masterNodeId(leader.getId());
        DiscoveryNode mixedNode1 = newNode(nodeId++, DiscoveryNodeRole.DATA_HOT_NODE_ROLE, DiscoveryNodeRole.DATA_WARM_NODE_ROLE);
        discoBuilder.add(mixedNode1);
        DiscoveryNode mixedNode2 = newNode(nodeId++, DiscoveryNodeRole.DATA_HOT_NODE_ROLE, DiscoveryNodeRole.DATA_WARM_NODE_ROLE);
        discoBuilder.add(mixedNode2);
        DiscoveryNode mixedNode3 = newNode(nodeId, DiscoveryNodeRole.DATA_HOT_NODE_ROLE, DiscoveryNodeRole.DATA_WARM_NODE_ROLE);
        discoBuilder.add(mixedNode3);
        discoBuilder.localNodeId(mixedNode1.getId());
        
        Metadata.Builder metadataBuilder = Metadata.builder();
        RoutingTable.Builder routingTableBuilder = RoutingTable.builder();
        IndexMetadata hotIndex1 = indexMetadata("hot_index_1", 3, 1, DataTier.DATA_HOT);
        metadataBuilder.put(hotIndex1, false).generateClusterUuidIfNeeded();
        {
            IndexRoutingTable.Builder indexRoutingTableBuilder = IndexRoutingTable.builder(hotIndex1.getIndex());
            routeTestShardToNodes(hotIndex1, 0, indexRoutingTableBuilder, mixedNode1, mixedNode2);
            routeTestShardToNodes(hotIndex1, 1, indexRoutingTableBuilder, mixedNode3, mixedNode1);
            routeTestShardToNodes(hotIndex1, 2, indexRoutingTableBuilder, mixedNode2, mixedNode3);
            routingTableBuilder.add(indexRoutingTableBuilder.build());
        }
        IndexMetadata warmIndex1 = indexMetadata("warm_index_1", 1, 1, DataTier.DATA_WARM);
        metadataBuilder.put(warmIndex1, false).generateClusterUuidIfNeeded();