Doc: Fix various documentation warnings

- QList iterators are now nested classes inside QList.
- Drop reference to Qt OpenGL Widgets landing page, there is no such
  page.
- Fix typos and linking issues.

Fixes: QTBUG-86295
Change-Id: I964843deb81aa55ff8ddb9a1c2b004cb72e68de9
Reviewed-by: Topi Reiniö <topi.reinio@qt.io>
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
(cherry picked from commit 99abdd180bd6f626f4ca94806fdaddbeb3774325)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/kernel/qobject.cpp

@@ -4206,7 +4206,7 @@ QDebug operator<<(QDebug dbg, const QObject *o)
 
     This macro associates extra information to the class, which is available
     using QObject::metaObject(). Qt makes only limited use of this feature in
-    \l{Qt D-Bus} and \l{Qt QML module}{Qt QML}.
+    \l{Qt D-Bus} and \l{Qt QML} modules.
 
     The extra information takes the form of a \a Name string and a \a Value
     literal string.

src/corelib/tools/qlist.qdoc

@@ -1381,10 +1381,9 @@
     \overload
 */
 
-/*! \typedef QList::iterator
-
-    The QList::iterator typedef provides an STL-style non-const
-    iterator for QList and QStack.
+/*! \class QList::iterator
+    \inmodule QtCore
+    \brief Provides an STL-style non-const iterator for QList and QStack.
 
     QList provides both \l{STL-style iterators} and \l{Java-style
     iterators}.
@@ -1403,10 +1402,9 @@
     \sa QList::begin(), QList::end(), QList::const_iterator, QMutableListIterator
 */
 
-/*! \typedef QList::const_iterator
-
-    The QList::const_iterator typedef provides an STL-style const
-    iterator for QList and QStack.
+/*! \class QList::const_iterator
+    \inmodule QtCore
+    \brief Provides an STL-style const iterator for QList and QStack.
 
     QList provides both \l{STL-style iterators} and \l{Java-style
     iterators}.

src/corelib/tools/qvarlengtharray.qdoc

@@ -775,7 +775,7 @@
     This function requires the value type to have an implementation
     of \c operator==().
 
-    \sa operator!=()
+    \sa {operator!=(const QVarLengthArray<T, Prealloc1> &left, const QVarLengthArray<T, Prealloc2> &right)}{operator!=()}
 */
 
 /*! \fn template<typename T, qsizetype Prealloc1, qsizetype Prealloc2> bool operator!=(const QVarLengthArray<T, Prealloc1> &left, const QVarLengthArray<T, Prealloc2> &right)
@@ -790,7 +790,7 @@
     This function requires the value type to have an implementation
     of \c operator==().
 
-    \sa operator==()
+    \sa {operator==(const QVarLengthArray<T, Prealloc1> &left, const QVarLengthArray<T, Prealloc2> &right)}{operator==()}
 */
 
 /*! \fn template<typename T, qsizetype Prealloc1, qsizetype Prealloc2> bool operator<(const QVarLengthArray<T,Prealloc1> &lhs, const QVarLengthArray<T,Prealloc2> &rhs)

src/opengl/doc/src/qtopengl-module.qdoc

@@ -52,7 +52,4 @@
     \title Qt OpenGL Widgets C++ Classes
     \qtcmakepackage OpenGLWidgets
     \qtvariable openglwidgets
-
-    The \l{Qt OpenGL Widgets} page contains information about how to use the
-    module.
 */

src/widgets/doc/src/qtwidgets.qdoc

@@ -34,6 +34,6 @@
 
     \brief The Qt Widgets module extends Qt GUI with C++ widget functionality.
 
-    The \l{Qt Widget} page contains information about how to use the module.
+    The \l{Qt Widgets} page contains information about how to use the module.
 */