QMenus should allow tooltips

Currently, Qt doesn't directly support tooltips being shown for QMenu objects. Tooltips in menu options are commonly useful in "Recent Files" menus, where users are often presented with a list of Recent Files with a tooltip describing each file's full path.

This request is closely related to QTBUG-2362 – but maybe it's better suited as a "Suggestion" than a "Bug"? That bug was closed on the reasoning that it would typically be annoying to present tooltips in a menu since the tooltip would just echo the action label. However, I think this concern could be addressed by making the default behavior for a QMenu be to not show tooltips and to require an explicit request by the programmer to show tooltips.

I was able work around this limitation by using the QMenu's hovered signal to change the menu's tooltip each time a different action is hovered over, but this seems like something that could be directly supported in Qt.