Gui: support toolbar drag and drop to status bar and menu bar (#13571)

* Gui: support toolbar drag and drop to status bar and menu bar

Closes FreeCAD/FreeCAD#12979

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Gui: improve toolbar handling in status and menu bar

* Gui: fix workbench tab bar orientation in status or menu bar

* Gui: remove workbench toolbar position settings

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

src/Gui/MenuManager.h

@@ -79,7 +79,6 @@ class GuiExport MenuManager
 public:
     /** Sets up the menus of a given workbench. */
     void setup(MenuItem*) const;
-    void setupMenuBarCornerWidgets() const;
     /// sets up a context menu out of item
     void setupContextMenu(MenuItem* item, QMenu &menu) const;
     void retranslate() const;