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/testresult.cpp

@@ -100,7 +100,7 @@ Result::Type TestResult::toResultType(int rt)
     if (rt < Result::FIRST_TYPE || rt > Result::LAST_TYPE)
         return Result::Invalid;
 
-    return (Result::Type)rt;
+    return Result::Type(rt);
 }
 
 QString TestResult::resultToString(const Result::Type type)