Utils: Add "Layouting::HorizontalRule" LayoutItem

We have many horizontal separator lines in the UI, which are each time
repetitively created from a QFrame with some flags set. With the .ui
inlining, we will have more of these separators coming.

This change intoduces a Layouting::HorizontalRule LayoutItem and
replaces various existing QFarme separators with it.

Change-Id: I60bad89e2a2b777fbd2f9d0cf872af81e41dcfd7
Reviewed-by: hjk <hjk@qt.io>

src/plugins/ios/iossettingswidget.cpp

@@ -19,7 +19,6 @@
 #include <QApplication>
 #include <QCheckBox>
 #include <QDateTime>
-#include <QFrame>
 #include <QGroupBox>
 #include <QHeaderView>
 #include <QInputDialog>
@@ -71,10 +70,6 @@ IosSettingsWidget::IosSettingsWidget()
     m_resetButton->setEnabled(false);
     m_resetButton->setToolTip(tr("Reset contents and settings of simulator devices."));
 
-    auto line = new QFrame;
-    line->setFrameShadow(QFrame::Raised);
-    line->setFrameShape(QFrame::HLine);
-
     auto createButton = new QPushButton(tr("Create"));
     createButton->setToolTip(tr("Create a new simulator device."));
 
@@ -121,7 +116,7 @@ IosSettingsWidget::IosSettingsWidget()
                         st
                     },
                 },
-                line,
+                HorizontalRule {},
                 Row { tr("Screenshot directory:"), m_pathWidget }
             }
         }