JNI: convert to and from JNI types for callObjectMethod as well

While we can probably deprecate this function, with the change of
Q_DECLARE_JNI_CLASS'ed types to be QJniObjects we need to correctly
translate from e.g. jobject to QJniObject.

Amends 62cb5589b3.

Change-Id: Id3c23fc0724e2eff895029b694d418481abcb8e6
Reviewed-by: Assam Boudjelthia <assam.boudjelthia@qt.io>
Reviewed-by: Petri Virkkunen <petri.virkkunen@qt.io>

src/corelib/kernel/qjniobject.h

@@ -148,7 +148,9 @@ public:
     {
         QtJniTypes::assertObjectType<Ret>();
         constexpr auto signature = QtJniTypes::methodSignature<Ret, Args...>();
-        return callObjectMethod(methodName, signature.data(), std::forward<Args>(args)...);
+        LocalFrame<Args...> frame;
+        return frame.template convertFromJni<Ret>(callObjectMethod(methodName, signature,
+                                            frame.convertToJni(std::forward<Args>(args))...));
     }
 
     QJniObject callObjectMethod(const char *methodName, const char *signature, ...) const;