TreeModel: Add a StaticTreeItem(QString) convenience constructor

Covers the common case and hopefully avoids the recurring MSVC
problem with initializer lists in this location.

Change-Id: I1b2bbb083f9fc86af3b51b8f52615fb70c832b95
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Tim Jenssen <tim.jenssen@theqtcompany.com>

src/libs/utils/treemodel.cpp

@@ -1054,6 +1054,11 @@ StaticTreeItem::StaticTreeItem(const QStringList &displays)
 {
 }
 
+StaticTreeItem::StaticTreeItem(const QString &display)
+    : m_displays(display)
+{
+}
+
 QVariant StaticTreeItem::data(int column, int role) const
 {
     if (role == Qt::DisplayRole && column >= 0 && column < m_displays.size())