AutoTest: Code cosmetics

* use nullptr
* override
* remove old style casts
* fix most of the code model warnings

Change-Id: Ia08e846f9326ae28ca7e7d66748e25a8b817b9b1
Reviewed-by: Xing Xiong
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/autotest/testrunner.h

@@ -52,12 +52,11 @@ namespace Internal {
 class AUTOTESTSHARED_EXPORT TestRunner : public QObject
 {
     Q_OBJECT
-
 public:
     enum CancelReason { UserCanceled, Timeout, KitChanged };
 
     static TestRunner* instance();
-    ~TestRunner();
+    ~TestRunner() override;
 
     void setSelectedTests(const QList<TestConfiguration *> &selected);
     void runTest(TestRunMode mode, const TestTreeItem *item);