Hide KHamburgerMenu in QMenus when a native menu bar is used
This in practice hides the "Menu" action in context menus in Dolphin when a native menu bar like a global menu bar or a menu title bar button is used. Even before this change, the "Menu" action in context menus was only visible if the hamburger menu wasn't visible on a toolbar and the in-window menu bar was hidden.
Aside from Dolphin this can also be tested with graphics/okular!463 (merged).
When a native menu bar is used, users normally don't need an additional KHamburgerMenu in any QMenus.
This was already once before the behaviour in this scenario but it was unnecessarily changed as a side-effect of 901b049c.
While the m_menuAction can be used as a normal menu by users that don't mind invoking a QMenu to access any menu actions, its primary use really is that of a fallback. Therefore the existence of a native menu bar (no matter what shape or size it might have) is enough reason for us to hide m_menuAction.
FIXED-IN: 5.86