Global tool for discovering an app's platform dependencies

### Summary

A .NET project is where the dependencies become calculable. By running a tool against a project, and using the collected platform dependency data, it is possible to definitively output the list of platform dependencies that project requires. This greatly reduces the friction required to gather this information when compared to either the trial-and-error method of running the app and seeing whether it breaks or manually looking up .NET components to determine their platform dependencies.

> Note: This is a proposed experience for .NET 6 and not yet committed.

### Goal

Developers can discover their application's platform dependencies in a deterministic fashion by running a dotnet global tool.