Fix column profiling to use query folding

Hi,

when one enables column profiling in Power BI (tested with the databricks Connector) by enabling "View" -> "Column distribution" in the PowerQuery window and then wants to sample the whole data set by selecting this at the very bottom of the window Power BI sends a select query without any grouping to the datasource.
As a result this does not work on any big data scenario.

I would expect Power BI to use its folding capabilities and create a query that is folded to the data source so that instead of retrieving billions of rows just the statistics are retrieved by Power BI.

Thanks