[VS Code] Add "Go to source" action for source-backed resources #20424

Summary

Source-backed Aspire resources, such as a .NET project, should expose a Go to source action in the VS Code extension.

Selecting the action would switch focus to the VS Code Explorer and reveal/select the resource's source location. For a .NET project resource, this could select the project file or project directory.

Motivation

The Aspire resource view is useful for understanding and operating a distributed application, but moving from a running resource back to its implementation currently requires manually finding the corresponding project in the workspace.

This becomes increasingly cumbersome in larger solutions, multi-root workspaces, and applications containing similarly named projects. The resource already has source metadata, so the extension can provide a direct navigation path.

Proposed experience

Add Go to source to the context menu or actions for resources that have a local source location.

When invoked, the extension should:

1. Resolve the resource's source path.
2. Switch focus to the VS Code Explorer.
3. Reveal and select the source location.

For example:

• .NET project resource: reveal the .csproj or its containing directory.
• JavaScript/Python source-backed resource: reveal the configured project/application directory.
• Executable resource with a workspace source path: reveal the corresponding file or working directory where possible.

Expected behavior

• The action is shown only when the resource has a resolvable local source path.
• Paths are resolved correctly for multi-root workspaces and worktrees.
• If the source is outside the current workspace or no longer exists, the extension reports a clear message rather than silently doing nothing.
• Selecting the action does not open a duplicate workspace or modify the current Aspire session.

Possible placement

• Resource context menu: Go to source
• Resource details/action toolbar

The context-menu option would provide the most direct equivalent to existing VS Code navigation actions such as revealing a file in the Explorer.