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
CoordinationMetadata originalMeta = new CoordinationMetadata(
            randomNonNegativeLong(),
            randomVotingConfig(),
            randomVotingConfig(),
            randomVotingConfigExclusions()
        );
        Metadata metadata = Metadata.builder().coordinationMetadata(originalMeta).build();
        final XContentBuilder builder = JsonXContent.contentBuilder();
        builder.startObject();
        Metadata.FORMAT.toXContent(builder, metadata);
        builder.endObject();
        try (XContentParser parser = createParser(JsonXContent.jsonXContent, BytesReference.bytes(builder))) {
            final CoordinationMetadata fromXContentMeta = Metadata.fromXContent(parser).coordinationMetadata();
            assertThat(fromXContentMeta, equalTo(originalMeta));
        }
    }
    public void testGlobalStateEqualsCoordinationMetadata() {
        CoordinationMetadata coordinationMetadata1 = new CoordinationMetadata(
            randomNonNegativeLong(),
            randomVotingConfig(),
            randomVotingConfig(),
            randomVotingConfigExclusions()
        );
        Metadata metadata1 = Metadata.builder().coordinationMetadata(coordinationMetadata1).build();
        CoordinationMetadata coordinationMetadata2 = new CoordinationMetadata(
            randomNonNegativeLong(),
            randomVotingConfig(),
            randomVotingConfig(),
            randomVotingConfigExclusions()
        );