QmlDesigner: Focus the content widget of the dock when focusing tab

When DockWidgetTab or DockWidget is focused, typically user actually
wants to focus the content widget, so we now do that.
Focusing content widget is done asynchronously to avoid complications
from doing another setFocus in middle of setFocus handling.

Fixes: QDS-9104
Change-Id: I569639c2f36f0721aafcdcab3498c875e98993a9
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>
Reviewed-by: Mahmoud Badri <mahmoud.badri@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

src/libs/advanceddockingsystem/dockfocuscontroller.cpp

@@ -162,6 +162,8 @@ namespace ADS
         if (!dockWidget)
             dockWidget = qobject_cast<DockWidget *>(focusedNow);
 
+        bool focusActual = dockWidget && dockWidget->widget();
+
         if (!dockWidget)
             dockWidget = internal::findParent<DockWidget *>(focusedNow);
 
@@ -174,6 +176,12 @@ namespace ADS
     #endif
 
         d->updateDockWidgetFocus(dockWidget);
+
+        if (focusActual) {
+            // Do this async to avoid issues when changing focus in middle of another focus handling
+            QMetaObject::invokeMethod(dockWidget->widget(), QOverload<>::of(&QWidget::setFocus),
+                                      Qt::QueuedConnection);
+        }
     }
 
     void DockFocusController::setDockWidgetFocused(DockWidget *focusedNow)