Implement a strategy to select the assets to publish per vertical

[ViktorHofer]

Verticals produce duplicate assets, i.e. nuget packages like System.CommandLine.nupkg. We need a strategy to select assets per vertical to publish to BAR. A good default might be to publish all nuget packages by default on win-x64 and only publish others that don't exist on win-x64.

I assume that this asset selection strategy needs to run in the join point at the very end after all the verticals.

cc @mmitche

[mmitche]

I also suggest that we include an error condition if asset X doesn't exist on the default vertical, but does exist in multiple other verticals. A choice would be required.

[mmitche]

Assigned to @MilenaHristova

[pavel-purma]

Asset selection is already done. I will continue on publishing part