Change the get data stream api to include the following properties of a data stream:

- ~~Add `index_mode` from `DataStream` to the response.~~
- For each backing index of a data stream with time series index mode, include the temporal range the backing index represents (based on the `index.time_series.start_time` and `index.time_series.end_time` index settings.
modules/data-streams/src/test/java/org/elasticsearch/datastreams/action/GetDataStreamsResponseTests.java
@Override
    protected Writeable.Reader<Response> instanceReader() {
        return Response::new;
    }
    @Override
    protected Response createTestInstance() {
        int numDataStreams = randomIntBetween(0, 8);
        List<Response.DataStreamInfo> dataStreams = new ArrayList<>();
        for (int i = 0; i < numDataStreams; i++) {
            dataStreams.add(
                new Response.DataStreamInfo(
                    DataStreamTestHelper.randomInstance(),
                    ClusterHealthStatus.GREEN,
                    randomAlphaOfLengthBetween(2, 10),
                    randomAlphaOfLengthBetween(2, 10)
                )
            );
        }
        return new Response(dataStreams);
    }
}