[ES|QL] Add Fast Query Analytics toggle to the editor footer

[stratoula]

Summary

Closes #254858

Adds an approximateResultsControl prop to the ES|QL editor. When provided, a "Fast results" toggle appears in the editor footer that opens a popover with an On/Off button group. The editor does not act on this setting itself -- it propagates the selected value to consumers so they can include the approximate results option in the _query request.

Consumer usage

const [approximateResults, setApproximateResults] = useState(false);

<ESQLEditor
  approximateResultsControl={{
    enabled: approximateResults,
    onChange: setApproximateResults,
  }}
/>

The toggle is hidden when the prop is not provided.

Checklist

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

[elasticmachine]

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