Move qt_error_string to qlogging.h

qcontainerfwd.h was relying on the forward declaration of QString in
qglobal.h, so add the missing forward declaration there.

Task-number: QTBUG-99313
Change-Id: Id3ecaed5ce3b64dabb8454647a43d1520d30e713
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/corelib/global/qglobal.h

@@ -633,10 +633,6 @@ Q_CORE_EXPORT Q_DECL_CONST_FUNCTION bool qSharedBuild() noexcept;
 #  define QT_DEBUG
 #endif
 
-class QString;
-Q_DECL_COLD_FUNCTION
-Q_CORE_EXPORT QString qt_error_string(int errorCode = -1);
-
 #ifndef Q_CC_MSVC
 Q_NORETURN
 #endif

src/corelib/global/qlogging.h

@@ -172,5 +172,8 @@ Q_CORE_EXPORT void qSetMessagePattern(const QString &messagePattern);
 Q_CORE_EXPORT QString qFormatLogMessage(QtMsgType type, const QMessageLogContext &context,
                                         const QString &buf);
 
+Q_DECL_COLD_FUNCTION
+Q_CORE_EXPORT QString qt_error_string(int errorCode = -1);
+
 QT_END_NAMESPACE
 #endif // QLOGGING_H

src/corelib/tools/qcontainerfwd.h

@@ -27,6 +27,7 @@ template <typename T> class QSet;
 template <typename T> class QStack;
 template <typename T, qsizetype Prealloc = 256> class QVarLengthArray;
 template <typename T> class QList;
+class QString;
 #ifndef Q_CLANG_QDOC
 template<typename T> using QVector = QList<T>;
 using QStringList = QList<QString>;