ProjectExplorer: Move use of some knowledge from KitAspectWidget to KitAspect

Essentially a follow-up to 09a7d2bd45.

Change-Id: I4dd9d64eec77ddf9cdccbac808e9a0978b9986bf
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/qmakeprojectmanager/qmakekitinformation.cpp

@@ -53,7 +53,7 @@ public:
         : KitAspectWidget(k, ki), m_lineEdit(new QLineEdit)
     {
         refresh(); // set up everything according to kit
-        m_lineEdit->setToolTip(toolTip());
+        m_lineEdit->setToolTip(ki->description());
         connect(m_lineEdit, &QLineEdit::textEdited, this, &QmakeKitAspectWidget::mkspecWasChanged);
     }