Turn webEngineLoadingInfo into a well-behaved value type

Add a default constructor so that QMetaType can create it.

Task-number: QTBUG-108649
Task-number: QTBUG-135032
Pick-to: 6.9 6.8
Change-Id: I9390392f24f29cc16e0f36367a6a77e60a76b068
Reviewed-by: Kaloyan Chehlarski <[email protected]>
Reviewed-by: Michal Klocek <[email protected]>

Author: Ulf Hermann

src/core/api/qwebengineloadinginfo.h

@@ -51,6 +51,7 @@ class Q_WEBENGINECORE_EXPORT QWebEngineLoadingInfo
     };
     Q_ENUM(ErrorDomain)
 
+    QWebEngineLoadingInfo() : QWebEngineLoadingInfo(QUrl(), LoadStartedStatus) {}
     QWebEngineLoadingInfo(const QWebEngineLoadingInfo &other);
     QWebEngineLoadingInfo &operator=(const QWebEngineLoadingInfo &other);
     QWebEngineLoadingInfo(QWebEngineLoadingInfo &&other);