Currently it is possible to migrate an existing data stream to a time series data stream.
This is done by updating the index template that created the data stream. 
Then after a rollover the data stream is a time series data stream. 

Via a similar way it should be possible to change time series data stream back 
to a regular data stream. Currently when changing the `index.mode` setting
on an index template from `time_series` to `standard` (or removing the setting)
results in a validation error.
modules/data-streams/src/javaRestTest/java/org/elasticsearch/datastreams/TsdbDataStreamRestIT.java
"rx": 530605511
                    }
                }
            }
        }
        """;
    private static final String BULK =
        """
            {"create": {}}
            {"@timestamp": "$now", "metricset": "pod", "k8s": {"pod": {"name": "cat", "uid":"947e4ced-1786-4e53-9e0c-5c447e959507", "ip": "10.10.55.1", "network": {"tx": 2001818691, "rx": 802133794}}}}
            {"create": {}}
            {"@timestamp": "$now", "metricset": "pod", "k8s": {"pod": {"name": "hamster", "uid":"947e4ced-1786-4e53-9e0c-5c447e959508", "ip": "10.10.55.1", "network": {"tx": 2005177954, "rx": 801479970}}}}
            {"create": {}}
            {"@timestamp": "$now", "metricset": "pod", "k8s": {"pod": {"name": "cow", "uid":"947e4ced-1786-4e53-9e0c-5c447e959509", "ip": "10.10.55.1", "network": {"tx": 2006223737, "rx": 802337279}}}}
            {"create": {}}
            {"@timestamp": "$now", "metricset": "pod", "k8s": {"pod": {"name": "rat", "uid":"947e4ced-1786-4e53-9e0c-5c447e959510", "ip": "10.10.55.2", "network": {"tx": 2012916202, "rx": 803685721}}}}
            {"create": {}}
            {"@timestamp": "$now", "metricset": "pod", "k8s": {"pod": {"name": "dog", "uid":"df3145b3-0563-4d3b-a0f7-897eb2876ea9", "ip": "10.10.55.3", "network": {"tx": 1434521831, "rx": 530575198}}}}
            {"create": {}}
            {"@timestamp": "$now", "metricset": "pod", "k8s": {"pod": {"name": "tiger", "uid":"df3145b3-0563-4d3b-a0f7-897eb2876ea10", "ip": "10.10.55.3", "network": {"tx": 1434577921, "rx": 530600088}}}}
            {"create": {}}
            {"@timestamp": "$now", "metricset": "pod", "k8s": {"pod": {"name": "lion", "uid":"df3145b3-0563-4d3b-a0f7-897eb2876e11", "ip": "10.10.55.3", "network": {"tx": 1434587694, "rx": 530604797}}}}
            {"create": {}}
            {"@timestamp": "$now", "metricset": "pod", "k8s": {"pod": {"name": "elephant", "uid":"df3145b3-0563-4d3b-a0f7-897eb2876eb4", "ip": "10.10.55.3", "network": {"tx": 1434595272, "rx": 530605511}}}}
            """;
    @Before
    public void setup() throws IOException {
        
        var request = new Request("POST", "/_component_template/custom_template");
        request.setJsonEntity(COMPONENT_TEMPLATE);