Meson: Hide the tool aspect implementation

Change-Id: Ib8cf56385d7e369a2c185d6cbd62613b4b28bc79
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

src/plugins/mesonprojectmanager/mesonbuildsystem.cpp

@@ -6,8 +6,8 @@
 #include "kitdata.h"
 #include "mesonbuildconfiguration.h"
 #include "mesonprojectmanagertr.h"
-#include "mesontoolkitaspect.h"
 #include "settings.h"
+#include "toolkitaspectwidget.h"
 
 #include <coreplugin/icore.h>
 
@@ -24,8 +24,6 @@
 #include <utils/macroexpander.h>
 #include <utils/qtcassert.h>
 
-#include <optional>
-
 #include <QLoggingCategory>
 
 #define LEAVE_IF_BUSY() \