### 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/main/java/org/elasticsearch/xpack/core/DataTiersUsageTransportAction.java
threadPool,
            actionFilters,
            indexNameExpressionResolver
        );
        this.client = client;
    }
    @Override
    protected void masterOperation(
        Task task,
        XPackUsageRequest request,
        ClusterState state,
        ActionListener<XPackUsageFeatureResponse> listener
    ) {
        client.admin()
            .cluster()
            .prepareNodesStats()
            .all()
            .setIndices(CommonStatsFlags.ALL)
            .execute(ActionListener.wrap(nodesStatsResponse -> {
                final RoutingNodes routingNodes = state.getRoutingNodes();
                final ImmutableOpenMap<String, IndexMetadata> indices = state.getMetadata().getIndices();
                
                Map<String, String> indicesToTiers = tierIndices(indices);
                
                Map<String, DataTiersFeatureSetUsage.TierSpecificStats> tierSpecificStats = calculateStats(
                    nodesStatsResponse.getNodes(),
                    indicesToTiers,
                    routingNodes
                );
                listener.onResponse(new XPackUsageFeatureResponse(new DataTiersFeatureSetUsage(tierSpecificStats)));