terminal-manager view conflicts with tabbed terminal layout

[ndoschek]

Bug Description:

Follow up of GH-16604

When terminal.grouping.mode is set to tabbed (current default), the Terminal Manager view should not be visible or enabled. If the Terminal Manager is opened in this mode, terminal-related commands such as "New Terminal" do not behave correctly.

And secondly, switching the setting back to tabbed and closing the Terminal Manager results in the "New Terminal" command not opening a terminal, while the following error is logged:

Uncaught (in promise) Error: Reference widget is not in the layout.
at te.addWidget (docklayout.ts:386:13)
at c.addWidget (dockpanel.ts:408:35)
at c.addWidget (theia-dock-panel.ts:196:15)
at c.addWidget (application-shell.ts:991:34)
at E.open (terminal-frontend-contribution.ts:956:24)
at E.openTerminal (terminal-frontend-contribution.ts:1032:18)
at async u.executeCommand (command.ts:341:19)

Steps to Reproduce:

A)

1. Ensure terminal.grouping.mode is set to tabbed.
2. Open the Terminal Manager view (via Menu View > Open View > Terminal manager)
3. Attempt to create a new terminal (via command palette or Terminal Menu)

B)

1. Ensure terminal.grouping.mode is set to tree and open the Terminal manager view.
2. Switch the setting back to tabbed close the Terminal Manager
3. Use menu Terminal > New Terminal and observe no terminal is opened and the above error is logged in the console.

Additional Information

• Operating System: all
• Theia Version: >= 1.67.0