Datasource panel's column chart is aggregated on the backend

[mscolnick]

Description

Similar to #3104

Currently we send up to 20k rows of data to the frontend to aggregate columns summaries. This aggregation happens in vega-lite and can cause memory issues and slowdowns.

Suggested solution

We would like to move this aggregation to the backend either using vega-fusion (if installed) or narwhals.Expr.hist (if/when implemented).

Alternative

No response

Additional context

This could help: narwhals-dev/narwhals#1561

[mscolnick]

This can now be handled by #4068

I will keep this open in case we want to handle this without the extra dependency needed.