Missing context keys from the when clause contexts page

[racz16]

The following context keys are missing from the when clause contexts page, but are mentioned in other pages:

• virtualWorkspace (Virtual Workspaces, Web Extensions)
• shellExecutionSupported (Web Extensions, Task Provider)
• processExecutionSupported (Task Provider)
• customExecutionSupported (Task Provider)
• isWorkspaceTrusted (Workspace Trust)
• webviewSection (Webview)
• scmProvider (Source Control)
• scmResourceGroup (Source Control)
• originalResourceScheme (Source Control)
• testId (Testing)
• controllerId (Testing)
• testItemHasUri (Testing)