[Lens] Update grouping editor to indicate the expected result of a grouping change

[wylieconlon]

Date histograms will always have the same values, regardless of the grouping order. Other aggregations are more strongly affected by the grouping order, especially the Terms aggregation. I propose that the grouping editor for date histograms should reflect the changes in the other operation, not in the date order. A quick mock-up of this:

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)