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
}
    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/63973")
    public void testDatafeedTimingStats_DatafeedRecreated() throws Exception {
        client().admin().indices().prepareCreate("data").setMapping("time", "type=date").get();
        long numDocs = randomIntBetween(32, 2048);
        Instant now = Instant.now();
        indexDocs(logger, "data", numDocs, now.minus(Duration.ofDays(14)).toEpochMilli(), now.toEpochMilli());
        Job.Builder job = createScheduledJob("lookback-job-datafeed-recreated");
        String datafeedId = "lookback-datafeed-datafeed-recreated";
        DatafeedConfig datafeedConfig = createDatafeed(datafeedId, job.getId(), Collections.singletonList("data"));
        putJob(job);
        CheckedRunnable<Exception> openAndRunJob = () -> {
            openJob(job.getId());
            assertBusy(() -> assertEquals(getJobStats(job.getId()).get(0).getState(), JobState.OPENED));
            putDatafeed(datafeedConfig);
            
            assertDatafeedStats(datafeedId, DatafeedState.STOPPED, job.getId(), equalTo(0L));
            startDatafeed(datafeedId, 0L, now.toEpochMilli());
            assertBusy(() -> {
                assertThat(getDataCounts(job.getId()).getProcessedRecordCount(), equalTo(numDocs));
                
                assertDatafeedStats(datafeedId, DatafeedState.STOPPED, job.getId(), greaterThan(0L));
            }, 60, TimeUnit.SECONDS);
            deleteDatafeed(datafeedId);
            waitUntilJobIsClosed(job.getId());
        };
        openAndRunJob.run();
        openAndRunJob.run();
    }
    public void testDatafeedTimingStats_QueryDelayUpdated_TimingStatsNotReset() throws Exception {