Since #87849 and #88534 it is possible that anomaly detection jobs and datafeeds will encounter the `aggregate_metric_double` type.

We need to investigate how this will affect certain aspects of their behaviour:

1. Specifying detector fields when the datafeed is using an aggregation
2. Specifying detector fields when the datafeed is not using an aggregation
3. Ability to switch a datafeed between using an aggregation and not using an aggregation without deleting and recreating the job
4. Correct identification of whether to use `_source` or doc values to get values from `aggregate_metric_double` fields
5. How to appropriately set `summary_count_field` when using `aggregate_metric_double`

Based on this investigation decide what changes we should make to either code or documentation.
x-pack/plugin/ml/qa/native-multi-node-tests/src/javaRestTest/java/org/elasticsearch/xpack/ml/integration/DatafeedJobsIT.java
}, 60, TimeUnit.SECONDS);
        stopDatafeed(datafeedConfig.getId());
        
        
        
        
        Thread.sleep(randomIntBetween(1, 9));
        KillProcessAction.Request killRequest = new KillProcessAction.Request(job.getId());
        client().execute(KillProcessAction.INSTANCE, killRequest).actionGet();
        
        
        waitUntilJobIsClosed(job.getId(), TimeValue.timeValueSeconds(2));
    }
    private void startRealtime(String jobId) throws Exception {
        startRealtime(jobId, null);
    }
    private void startRealtime(String jobId, Integer maxEmptySearches) throws Exception {
        client().admin().indices().prepareCreate("data").setMapping("time", "type=date").get();
        long now = System.currentTimeMillis();
        long numDocs1;
        if (maxEmptySearches == null) {
            numDocs1 = randomIntBetween(32, 2048);
            long lastWeek = now - 604800000;
            indexDocs(logger, "data", numDocs1, lastWeek, now);
        } else {
            numDocs1 = 0;
        }
        Job.Builder job = createScheduledJob(jobId);
        putJob(job);
        openJob(job.getId());