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
} else if (previous != null && current != null) {
                if (Objects.equals(previous.getAliases(), current.getAliases())) {
                    return;
                }
                for (var key : current.getAliases().keySet()) {
                    if (previous.getAliases().containsKey(key) == false) {
                        putAlias(key, current.getIndex());
                    }
                }
                for (var key : previous.getAliases().keySet()) {
                    if (current.getAliases().containsKey(key) == false) {
                        removeAlias(key, current.getIndex());
                    }
                }
            }
        }
        private Builder putAlias(String alias, Index index) {
            Objects.requireNonNull(alias);
            Objects.requireNonNull(index);
            Set<Index> indices = new HashSet<>(aliasedIndices.getOrDefault(alias, Set.of()));
            if (indices.add(index) == false) {
                return this; 
            }
            aliasedIndices.put(alias, Collections.unmodifiableSet(indices));
            return this;
        }
        private Builder removeAlias(String alias, Index index) {
            Objects.requireNonNull(alias);
            Objects.requireNonNull(index);
            Set<Index> indices = aliasedIndices.get(alias);