Dependencies downloaded from a registry show an empty folder in dependencies view

[adam-fowler]

Describe the bug
Dependencies downloaded from a SwiftPM registry show an empty folder in dependencies view and fail to display what version is being used.

To Reproduce
Steps to reproduce the behavior:

1. Add dependency to a Package that is downloaded from a swift package registry
2. Once resolve has finished checkout Package dependencies pane.
3. The package will be displayed, but it won't have a branch or version number and when you click to open the folder you'll find it is empty

Expected behavior
Dependencies downloaded from a SwiftPM registry are visible in VSCode

Additional context
SwiftPM registry dependencies are stored in a registry/downloads folder in the .build folder. Here is an example of an entry in the workspace-state.json

      {
        "basedOn" : null,
        "packageRef" : {
          "identity" : "hummingbird-project.hummingbird",
          "kind" : "registry",
          "location" : "hummingbird-project.hummingbird",
          "name" : "hummingbird-project.hummingbird"
        },
        "state" : {
          "name" : "registryDownload",
          "version" : "2.6.1"
        },
        "subpath" : "hummingbird-project/hummingbird/2.6.1"
      },