Valgrind: Move some memcheck auto tests into plugin

Due to changed dependencies it is nowadays necessary to have more
of the plugin infrastructure at hand. Moving memcheck related tests
to be able to execute them as QC plugin unit test.

Change-Id: Iab492b3cb87728425b950ca9387edf292d895350
Reviewed-by: hjk <hjk@qt.io>

src/plugins/valgrind/valgrindplugin.h

@@ -48,6 +48,8 @@ public:
     ShutdownFlag aboutToShutdown() override;
 
     static ValgrindGlobalSettings *globalSettings();
+private:
+    QList<QObject *> createTestObjects() const override;
 };
 
 } // namespace Internal