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
{
            AtomicInteger onNextIndexCalls = new AtomicInteger(0);
            Map<String, MappingMetadata> mappings = metadata.findMappings(
                new String[] { "index1" },
                MapperPlugin.NOOP_FIELD_FILTER,
                onNextIndexCalls::incrementAndGet
            );
            assertThat(mappings, aMapWithSize(1));
            assertIndexMappingsNotFiltered(mappings, "index1");
            assertThat(onNextIndexCalls.get(), equalTo(1));
        }
        {
            AtomicInteger onNextIndexCalls = new AtomicInteger(0);
            Map<String, MappingMetadata> mappings = metadata.findMappings(
                new String[] { "index1", "index2" },
                MapperPlugin.NOOP_FIELD_FILTER,
                onNextIndexCalls::incrementAndGet
            );
            assertThat(mappings, aMapWithSize(2));
            assertIndexMappingsNotFiltered(mappings, "index1");
            assertIndexMappingsNotFiltered(mappings, "index2");
            assertThat(onNextIndexCalls.get(), equalTo(2));
        }
    }
    public void testFindMappingsNoOpFilters() throws IOException {
        MappingMetadata originalMappingMetadata = new MappingMetadata(
            "_doc",
            XContentHelper.convertToMap(JsonXContent.jsonXContent, FIND_MAPPINGS_TEST_ITEM, true)
        );
        Metadata metadata = Metadata.builder()