Description of the new feature/enhancement

F6 is commonly used to cycle through layers of the UI tree. Windows Terminal doesn't do that. We should make Windows Terminal respect that.

Proposed technical implementation details (optional)

1. introduce a new action called moveRegion() bound to F6 by default
2. when pressed...
   • [context: terminal] move the focus to the tab row
   • [context: settings UI] move the focus to the navigation view pane (on the left), then to the tab row

This will definitely bring up issues with focus again, so keep a close eye on that when working on this.