Add a property to ToolBarLayout to control how to deal with item height
By default, items will now be constrained by the toolbar height, with smaller items centered. A property is exposed that allows controlling the behaviour, setting it either to always match the toolbar height or to never affect item height.
Fixes https://bugs.kde.org/show_bug.cgi?id=425675
This MR also contains a small fix for ToolBarLayout not handling actions with AlwaysHide properly.
Edited by Arjen Hiemstra