[vscode] Implement full Workspace Trust behavior

[martin-fleck-at]

Feature Description:

VS Code has support for Workspace Trust to let the user decide whether a specific folder/workspace is trusted and therefore extensions that need to work with the code inside it are allowed to do so. If a workspace is not trusted, it will run in restricted mode, disabling any extensions that do not support restricted mode.

User point of view: https://code.visualstudio.com/docs/editor/workspace-trust
Extension point of view: https://code.visualstudio.com/api/extension-guides/workspace-trust

A first implementation of this API was done in [x] where the goal was to implement the extension API to avoid crashing extensions that use it and to have a preference for it. However, the actual behavior of the Restricted Mode and it's effect on the extension was not was not implemented. However, it does affect quite a lot of areas:

• Tasks
• Debugging
• Workspace settings
• Extensions
• Custom UI

The goal of this task is to bring the full Workspace Trust behavior of VS Code into Theia.