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/main/java/org/elasticsearch/cluster/metadata/Metadata.java
/**
     * Returns all of the concrete indices that are open.
     */
    public String[] getConcreteAllOpenIndices() {
        return allOpenIndices;
    }
    /**
     * Returns all of the concrete indices that are open and not hidden.
     */
    public String[] getConcreteVisibleOpenIndices() {
        return visibleOpenIndices;
    }
    /**
     * Returns all of the concrete indices that are closed.
     */
    public String[] getConcreteAllClosedIndices() {
        return allClosedIndices;
    }
    /**
     * Returns all of the concrete indices that are closed and not hidden.
     */
    public String[] getConcreteVisibleClosedIndices() {
        return visibleClosedIndices;
    }
    /**
     * Returns indexing routing for the given <code>aliasOrIndex</code>. Resolves routing from the alias metadata used
     * in the write index.
     */
    public String resolveWriteIndexRouting(@Nullable String routing, String aliasOrIndex) {
        if (aliasOrIndex == null) {