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
.put(IndexMetadata.builder("index1").settings(indexSettings(IndexVersion.current(), 1, 0)).putMapping(originalMappingMetadata))
            .build();
        {
            Map<String, MappingMetadata> mappings = metadata.findMappings(
                new String[] { "index1" },
                MapperPlugin.NOOP_FIELD_FILTER,
                Metadata.ON_NEXT_INDEX_FIND_MAPPINGS_NOOP
            );
            MappingMetadata mappingMetadata = mappings.get("index1");
            assertSame(originalMappingMetadata, mappingMetadata);
        }
        {
            Map<String, MappingMetadata> mappings = metadata.findMappings(
                new String[] { "index1" },
                index -> field -> randomBoolean(),
                Metadata.ON_NEXT_INDEX_FIND_MAPPINGS_NOOP
            );
            MappingMetadata mappingMetadata = mappings.get("index1");
            assertNotSame(originalMappingMetadata, mappingMetadata);
        }
    }
    @SuppressWarnings("unchecked")
    public void testFindMappingsWithFilters() throws IOException {
        String mapping = FIND_MAPPINGS_TEST_ITEM;
        if (randomBoolean()) {
            Map<String, Object> stringObjectMap = XContentHelper.convertToMap(JsonXContent.jsonXContent, FIND_MAPPINGS_TEST_ITEM, false);
            Map<String, Object> doc = (Map<String, Object>) stringObjectMap.get("_doc");
            try (XContentBuilder builder = JsonXContent.contentBuilder()) {
                builder.map(doc);
                mapping = Strings.toString(builder);