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
"allClosedIndices",
            "visibleClosedIndices",
            "indicesLookup",
            "mappingsByHash",
            "oldestIndexVersion"
        );
        var diff = new HashSet<>(checkedForGlobalStateChanges);
        diff.removeAll(excludedFromGlobalStateCheck);
        
        assertEquals(checkedForGlobalStateChanges, diff);
        
        
        var unclassifiedFields = Arrays.stream(Metadata.class.getDeclaredFields())
            .filter(f -> Modifier.isStatic(f.getModifiers()) == false)
            .map(Field::getName)
            .filter(n -> (checkedForGlobalStateChanges.contains(n) || excludedFromGlobalStateCheck.contains(n)) == false)
            .collect(Collectors.toSet());
        assertThat(unclassifiedFields, empty());
    }
    public static Metadata randomMetadata() {
        return randomMetadata(1);
    }
    public static Metadata randomMetadata(int numDataStreams) {
        Metadata.Builder md = Metadata.builder()
            .put(buildIndexMetadata("index", "alias", randomBoolean() ? null : randomBoolean()).build(), randomBoolean())
            .put(
                IndexTemplateMetadata.builder("template" + randomAlphaOfLength(3))
                    .patterns(Arrays.asList("bar-*", "foo-*"))
                    .settings(Settings.builder().put("random_index_setting_" + randomAlphaOfLength(3), randomAlphaOfLength(5)).build())
                    .build()