The new RID-specific tools should support a fallback for framework dependent, RID-agnostic tools

[baronfel]

Is your feature request related to a problem? Please describe.

The new RID-specific tools feature is awesome, but it means that tool authors need to declare up front the RIDs they support in totality. Users running on RIDs that aren't compatible with the set of RIDs the user has chosen to build for are simply unable to run the tool at all. This was something that framework-dependent tools were really good at, but they don't have a place in the new tool scheme.

Describe the solution you'd like

I'd like to be able to package a framework-dependent, RID-agnostic version of a tool under the any RID, so that clients attempting to use a tool that also has RID-specific variants have a way to run the tool. This would mean that packaging the tool would:

• create a new <packageId>.any.<packageVersion>.nupkg package that
  • would have all of the content of the RID-agnostic tools today
  • would use the existing dotnet executor instead of the new executable executor
  • would not contain any RID-specific assets for the set of RIDs that are covered by RID-specific tool packages
• add an entry for the .any. package into the top-level package's DotNetTools.xml manifest.

Additional context

Add any other context or screenshots about the feature request here.