Documentation: Fix information on how to iterate over lists

Remove the outdated code used for QStringList and point
QStringList and QList to the containers page.

Task-number: QTBUG-108687
Change-Id: I6fae6410ca759f91da85832ddb9f24e8a0ce202b
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
(cherry picked from commit 4a6ce541c59cfaabb5c68066d0e19912032e48df)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/doc/snippets/qstringlist/main.cpp

@@ -22,24 +22,6 @@ Widget::Widget(QWidget *parent)
     fonts << "Courier" << "Verdana";
 //! [0b]
 
-//! [1]
-    for (int i = 0; i < fonts.size(); ++i)
-         cout << fonts.at(i).toLocal8Bit().constData() << Qt::endl;
-//! [1]
-
-//! [2]
-    QStringListIterator javaStyleIterator(fonts);
-    while (javaStyleIterator.hasNext())
-         cout << javaStyleIterator.next().toLocal8Bit().constData() << Qt::endl;
-//! [2]
-
-//! [3]
-    QStringList::const_iterator constIterator;
-    for (constIterator = fonts.constBegin(); constIterator != fonts.constEnd();
-           ++constIterator)
-        cout << (*constIterator).toLocal8Bit().constData() << Qt::endl;
-//! [3]
-
 //! [4]
     QString str = fonts.join(", ");
      // str == "Arial, Helvetica, Times, Courier"

src/corelib/text/qstringlist.cpp

@@ -84,25 +84,7 @@ QT_BEGIN_NAMESPACE
 
     \section1 Iterating Over the Strings
 
-    To iterate over a list, you can either use index positions or
-    QList's Java-style and STL-style iterator types:
-
-    Indexing:
-
-    \snippet qstringlist/main.cpp 1
-
-    Java-style iterator:
-
-    \snippet qstringlist/main.cpp 2
-
-    STL-style iterator:
-
-    \snippet qstringlist/main.cpp 3
-
-    The QStringListIterator class is simply a type definition for
-    QListIterator<QString>. QStringList also provide the
-    QMutableStringListIterator class which is a type definition for
-    QMutableListIterator<QString>.
+    See \l {Iterating over Containers}.
 
     \section1 Manipulating the Strings
 

src/corelib/tools/qlist.qdoc

@@ -129,21 +129,7 @@
     support \c operator==().  These requirements are documented on a
     per-function basis.
 
-    Like the other container classes, QList provides \l{Java-style iterators}
-    (QListIterator and QMutableListIterator) and \l{STL-style iterators}
-    (QList::const_iterator and QList::iterator). In practice, iterators are
-    handy when working with generic algorithms provided by \l{generic
-    algorithms}{Qt} and the C++ standard library. \l{Java-style iterators} are
-    provided for backwards compatibility, prefer \l{STL-style iterators} when
-    writing C++ code.
-
-    \note Iterators over a QList, and references to individual elements
-    within one, cannot be relied on to remain valid when any non-const method
-    of the QList is called. Accessing such an iterator or reference after
-    the call to a non-const method leads to undefined behavior. When stability
-    for iterator-like functionality is required, you should use indexes instead
-    of iterators as they are not tied to QList's internal state and thus do
-    not get invalidated.
+    For iterating over the items, see \l {Iterating over Containers}.
 
     In addition to QList, Qt also provides QVarLengthArray, a very
     low-level class with little functionality that is optimized for