Reevaluate how we embed assets for SOS-containing packages

Global tools were reworked to use `publish` as a precursor to package. The way we get assets of dependencies for projects for unit testing breaks this assumption since we create the layout manually using the `Copy` task. This gets the packaging logic confused and we have a colision of assets coming from two places, even though they are the same asset.

This was worked around in https://github.com/dotnet/diagnostics/pull/5559, but the real long term fix is to stop using `Copy` long term and just publish projects as needed instead of trying to emulate the behavior of partial publish. This might need some fixups in the config paths for tests, but is less likely to break on the long run.