Add Support for multiple projects in a workspace

[SharpEdgeMarshall]

This PR adds support to workspaces that contain multiple nested Pulumi projects.
It generates multiple launch configurations for each Pulumi project found inside the workspace folders (even nested ones).

Co-authored by: @mbovo

[EronWright]

Thanks @SharpEdgeMarshall for the contribution!

I wasn't sure about the performance implications, e.g. in the face of a node_modules directory. And I would like to ensure that the launch configuration name is simple and clear, especially in the simple case of a root-level project. I'll take this for a spin, e.g. against the pulumi-examples repository.

I'm curious whether you find the alternative solution - "Add Folder to Workspace..." - to be inconvenient.

[SharpEdgeMarshall]

Hi @EronWright, the problem with "add folder to workspace" is that we handle hundreds of pulumi projects, so having to add them individually is a bit messy.
We have "groups" of pulumi projects that shares the same .venv and we create a workspace root dir for each one of them.

[EronWright]

@SharpEdgeMarshall that's reasonable. Let me point out that, aside from the "automatic" debug configurations, you can also create launch configurations by hand.