A composable index template with no `template` defined in the body is mistakingly always assumed to not be a time series template. Even if it refers to a component template that has the `index.mode` setting set to `time_series` and the component template defines mappings with dimension fields or routing paths.

Incorrectly this causes to create a data stream with a tsdb index *without* time series start and end time settings set. The fact that this can happen is another bug and is being tracked #98833.

What should happen in this case is that a tsdb data stream is created with a valid tsdb backing index (with correctly generated time series start and end time settings).

This bug was found as part investigating #98792 and is the cause of that bug.
server/src/test/java/org/elasticsearch/cluster/metadata/MetadataTests.java
import java.util.Map;
import java.util.Objects;
import java.util.Set;
import java.util.SortedMap;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import static org.elasticsearch.cluster.metadata.DataStreamTestHelper.createBackingIndex;
import static org.elasticsearch.cluster.metadata.DataStreamTestHelper.createFirstBackingIndex;
import static org.elasticsearch.cluster.metadata.DataStreamTestHelper.newInstance;
import static org.elasticsearch.cluster.metadata.Metadata.Builder.assertDataStreams;
import static org.elasticsearch.test.LambdaMatchers.transformedItemsMatch;
import static org.hamcrest.Matchers.aMapWithSize;
import static org.hamcrest.Matchers.allOf;
import static org.hamcrest.Matchers.anEmptyMap;
import static org.hamcrest.Matchers.contains;
import static org.hamcrest.Matchers.containsInAnyOrder;
import static org.hamcrest.Matchers.containsString;
import static org.hamcrest.Matchers.empty;
import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.hasItems;
import static org.hamcrest.Matchers.hasKey;
import static org.hamcrest.Matchers.hasSize;
import static org.hamcrest.Matchers.is;
import static org.hamcrest.Matchers.not;
import static org.hamcrest.Matchers.notNullValue;
import static org.hamcrest.Matchers.nullValue;
import static org.hamcrest.Matchers.sameInstance;
import static org.hamcrest.Matchers.startsWith;
public class MetadataTests extends ESTestCase {