VS Code workspace related changes.

[aparnamichael]

• Project manually added to the liberty dashboard is not available once it is saved as a workspace  #386
• Prevent the projects data saved in global state from mistakingly used by different vs code sessions  #396
• Save multiple projects selected by the user for adding into the dashboard before the user saves it as a workspace #395
• Cannot clear the global state when the user closes the workspace from file menu #394
• Project manually added to the liberty dashboard is not available once it becomes an untitled workspace  #454