Test: Configuration and environment service cleanup

[bpasero]

• win @isidorn
• os x @weinand
• Linux @joaomoreno

In order to work on extension API for configuration management, quite some debt in configuration land and environment handling (cli) was removed and lots of code refactored. We should make sure that we did not introduce regressions while doing so in the areas touched:

• All our command line arguments passed to VS Code work as before and work for either no instance running or an existing instance running
• You can install extensions from the command line
• User settings are being picked up and apply live throughout the UI
• Workspace settings are being picked up and apply live throughout the UI
• Debug an extension and verify the extension settings it defines are picked up properly within the extension

[isidorn]

Debug an extension and verify the extension settings are picked up properly within the extension

@bpasero You mean the workspace and user settings inside the window where the extension is launched? Or what extension settings are you refering to?

[bpasero]

@isidorn settings defined by the extension itself.