[doc] QSharedPointer: add some missing docs

Added docs for
- move-ctor, -assignment operator
- move-construction and -assignment from QSP<X>
- qHash()

There's more stuff missing, but I declare 'twas enough qdoc wrangling
for this round.

The texts are taken from other smart pointer docs, esp. QESDP, so
they're consistent.

Fixes: QTBUG-83134
Fixes: QTBUG-63700
Change-Id: Iff980d043e1635ed6cfdd3113c68bc23f3a0bad7
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit 5dc0f52e7047ca5927e6741fda554cb090184b71)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/tools/qsharedpointer.cpp

@@ -442,6 +442,46 @@
     get a compiler error.
 */
 
+/*!
+    \fn template <class T> QSharedPointer<T>::QSharedPointer(QSharedPointer &&other)
+
+    Move-constructs a QSharedPointer instance, making it point at the same
+    object that \a other was pointing to.
+
+    \since 5.4
+*/
+
+/*!
+    \fn template <class T> QSharedPointer<T>::operator=(QSharedPointer &&other)
+
+    Move-assigns \a other to this QSharedPointer instance.
+
+    \since 5.0
+*/
+
+/*!
+    \fn template <class T> template <class X> QSharedPointer<T>::QSharedPointer(QSharedPointer<X> &&other)
+
+    Move-constructs a QSharedPointer instance, making it point at the same
+    object that \a other was pointing to.
+
+    This constructor participates in overload resolution only if \c{X*}
+    implicitly converts to \c{T*}.
+
+    \since 5.6
+*/
+
+/*!
+    \fn template <class T> template <class X> QSharedPointer<T>::operator=(QSharedPointer<X> &&other)
+
+    Move-assigns \a other to this QSharedPointer instance.
+
+    This assignment operator participates in overload resolution only if \c{X*}
+    implicitly converts to \c{T*}.
+
+    \since 5.6
+*/
+
 /*!
     \fn template <class T> QSharedPointer<T>::QSharedPointer(const QWeakPointer<T> &other)
 
@@ -895,6 +935,15 @@
     Const overload of sharedFromThis().
 */
 
+/*!
+    \fn template <class T> qHash(const QSharedPointer<T> &key, size_t seed)
+    \relates QSharedPointer
+
+    Returns the hash value for \a key, using \a seed to seed the calculation.
+
+    \since 5.0
+*/
+
 /*!
     \fn template <class T> template <class X> bool operator==(const QSharedPointer<T> &ptr1, const QSharedPointer<X> &ptr2)
     \relates QSharedPointer

src/corelib/tools/qsharedpointer.h

@@ -48,6 +48,11 @@ public:
     QSharedPointer<T> &operator=(QSharedPointer<T> &&other) noexcept;
     QSharedPointer<T> &operator=(const QWeakPointer<T> &other);
 
+    template <class X>
+    QSharedPointer(QSharedPointer<X> && other) noexcept;
+    template <class X>
+    QSharedPointer &operator=(QSharedPointer<X> && other) noexcept;
+
     void swap(QSharedPointer<T> &other) noexcept;
 
     QWeakPointer<T> toWeakRef() const;
@@ -69,6 +74,9 @@ public:
     static inline QSharedPointer<T> create(Args &&... args);
 };
 
+template <class T>
+size_t qHash(const QSharedPointer<T> &key, size_t seed = 0) noexcept;
+
 template <class T>
 class QWeakPointer
 {