Asset plots, by partitions view

[YegorStolyarov]

Currently by-partition plot groups assets with same partitions, showng the max value for each group.

This is very situative option to group items, and there is no more useful like sum() at least.

Maybe some more options to get value for each group could be added?

Easiest way - by adding a new optional parameter to AssetMaterialization logic, a callable type