### 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(hotStats.nodeCount, is(3));
        assertThat(hotStats.indexCount, is(1));
        assertThat(hotStats.totalShardCount, is(6));
        assertThat(hotStats.docCount, is(6 * docCount));
        assertThat(hotStats.totalByteCount, is(6 * byteSize));
        assertThat(hotStats.primaryShardCount, is(3));
        assertThat(hotStats.primaryByteCount, is(3 * byteSize));
        assertThat(hotStats.primaryByteCountMedian, is(byteSize)); 
        assertThat(hotStats.primaryShardBytesMAD, is(0L)); 
        DataTiersFeatureSetUsage.TierSpecificStats warmStats = tierSpecificStats.get(DataTier.DATA_WARM);
        assertThat(warmStats, is(notNullValue()));
        assertThat(warmStats.nodeCount, is(5));
        assertThat(warmStats.indexCount, is(2));
        assertThat(warmStats.totalShardCount, is(4));
        assertThat(warmStats.docCount, is(4 * docCount));
        assertThat(warmStats.totalByteCount, is(4 * byteSize));
        assertThat(warmStats.primaryShardCount, is(2));
        assertThat(warmStats.primaryByteCount, is(2 * byteSize));
        assertThat(warmStats.primaryByteCountMedian, is(byteSize)); 
        assertThat(warmStats.primaryShardBytesMAD, is(0L)); 
        DataTiersFeatureSetUsage.TierSpecificStats coldStats = tierSpecificStats.get(DataTier.DATA_COLD);
        assertThat(coldStats, is(notNullValue()));
        assertThat(coldStats.nodeCount, is(1));
        assertThat(coldStats.indexCount, is(3));
        assertThat(coldStats.totalShardCount, is(3));
        assertThat(coldStats.docCount, is(3 * docCount));
        assertThat(coldStats.totalByteCount, is(3 * byteSize));
        assertThat(coldStats.primaryShardCount, is(3));
        assertThat(coldStats.primaryByteCount, is(3 * byteSize));
        assertThat(coldStats.primaryByteCountMedian, is(byteSize));