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
b.put(
            IndexMetadata.builder("index1")
                .settings(indexSettings(IndexVersion.current(), 1, 0))
                .putAlias(new AliasMetadata.Builder("my-alias"))
        );
        addDataStream("d1", b);
        b.put("my-alias", "d1", null, null);
        e = expectThrows(IllegalStateException.class, b::build);
        assertThat(e.getMessage(), containsString("data stream alias and indices alias have the same name (my-alias)"));
    }
    public void testDataStreamAliasValidationRestoreScenario() {
        Metadata.Builder b = Metadata.builder();
        b.dataStreams(
            Map.of("my-alias", createDataStream("my-alias")),
            Map.of("my-alias", new DataStreamAlias("my-alias", List.of("my-alias"), null, null))
        );
        var e = expectThrows(IllegalStateException.class, b::build);
        assertThat(e.getMessage(), containsString("data stream alias and data stream have the same name (my-alias)"));
        b = Metadata.builder();
        b.dataStreams(
            Map.of("d1", createDataStream("d1"), "my-alias", createDataStream("my-alias")),
            Map.of("my-alias", new DataStreamAlias("my-alias", List.of("d1"), null, null))
        );
        e = expectThrows(IllegalStateException.class, b::build);
        assertThat(e.getMessage(), containsString("data stream alias and data stream have the same name (my-alias)"));
        b = Metadata.builder();
        b.put(
            IndexMetadata.builder("index1")
                .settings(indexSettings(IndexVersion.current(), 1, 0))
                .putAlias(new AliasMetadata.Builder("my-alias"))