Always consider autohide panels in the edit mode zoom
introduce a new property strictAvailableScreenRect which is the available screen rect, always excluding the panel geometries, also autohide panels This is used only by edit mode zoom, while everything else still uses availableScreenRect. This is necessary as before when going in edit mode the autohide panels were considered, so the available space on desktop layout changed on the fly when going in edit mode, making impossible to properly configure desktop widgets when an autohide panel is present
depends from plasma-desktop!2525 (merged)
(cherry picked from commit dd1df88f)