Add redacted forms of labelled SpatialAggregate/Flows

[jc-harrison]

The disaggregated forms of SpatialAggregate and Flows described in #4668 may need a slightly different approach for redaction, because in some cases individual per-category counts that are redacted could be inferred by comparing the remaining unredacted counts to the results of the equivalent non-disaggregated query.

One approach could be to drop the labels (and return a single, non-disaggregated count) for each location where any of the disaggregated counts are too small.

[Thingus]

Already exists for SpatialAggregate in #4668 - will look into implementing similar for #4696