[Metrics UI] Set includeTimeseries on Observability fetchData request

[simianhacker]

Summary

This PR closes #70695 by fixing the Metrics UI fetchData function so that it sets the includeTimeseries flag for the Snapshot API request.

Checklist

Delete any items that are not applicable to this PR.

• Unit or functional tests were updated or added to match the most common scenarios

[elasticmachine]

Pinging @elastic/logs-metrics-ui (Team:logs-metrics-ui)

[simianhacker]

@elasticmachine merge upstream

[kibanamachine]

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• continuous-integration/kibana-ci/pull-request
• Commit: 9bb1f4e

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• 💚 Build #58709 succeeded 7493894

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@elasticmachine merge upstream

[jasonrhodes]

@simianhacker do we have our Snapshot API roughly documented anywhere? What does "includeTimeseries" do here?

[simianhacker]

Not really but I can create some if you would like.

includeTimeseies adds the time series used to determine avg, value (last), and max to the metric object for the node. By default we return the last 5 buckets (which you can override with timeRange.lookback). If you send timeRange.ignoreLookback, then it will return all the buckets from the date histogram (for the time range). If you set forceInterval then it will use the interval in the timeRange object, otherwise it tries to use the interval from dataset.period of a sample document or falls back to 1 minute.

Each setting was added for a specific use case.