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/main/java/org/elasticsearch/cluster/metadata/Metadata.java
String[] allOpenIndices,
        String[] visibleOpenIndices,
        String[] allClosedIndices,
        String[] visibleClosedIndices,
        SortedMap<String, IndexAbstraction> indicesLookup,
        Map<String, MappingMetadata> mappingsByHash,
        IndexVersion oldestIndexVersion,
        Map<String, ReservedStateMetadata> reservedStateMetadata
    ) {
        this.clusterUUID = clusterUUID;
        this.clusterUUIDCommitted = clusterUUIDCommitted;
        this.version = version;
        this.coordinationMetadata = coordinationMetadata;
        this.transientSettings = transientSettings;
        this.persistentSettings = persistentSettings;
        this.settings = settings;
        this.hashesOfConsistentSettings = hashesOfConsistentSettings;
        this.indices = indices;
        this.aliasedIndices = aliasedIndices;
        this.customs = customs;
        this.templates = templates;
        this.totalNumberOfShards = totalNumberOfShards;
        this.totalOpenIndexShards = totalOpenIndexShards;
        this.allIndices = allIndices;
        this.visibleIndices = visibleIndices;
        this.allOpenIndices = allOpenIndices;
        this.visibleOpenIndices = visibleOpenIndices;
        this.allClosedIndices = allClosedIndices;
        this.visibleClosedIndices = visibleClosedIndices;
        this.indicesLookup = indicesLookup;