Merge branch 'ElementLinkMoveable' into 'master'

Make ElementLink `moveable`

See merge request atlas/athena!35674

Control/AthLinks/test/ElementLink_test.cxx

@@ -672,6 +672,9 @@ void test3 (SGTest::TestStore& store)
 
   TestStore::sgkey_t sgkey = store.stringToKey ("foocont3", fooclid);
 
+  //Add check to see if Element link optimized for std::vector expansion
+  static_assert(std::is_nothrow_move_constructible<ElementLink<FooCont>>::value);
+
   FooCont* foocont3 = new FooCont;
   for (int i=0; i < 4; i++)
     foocont3->push_back (new Foo(i+200));

Control/CxxUtils/CxxUtils/CachedPointer.h

@@ -70,8 +70,10 @@ public:
 
 
   /// Copy constructor.
-  CachedPointer (const CachedPointer& other);
+  CachedPointer (const CachedPointer& other) noexcept;
 
+  /// Move constructor.
+  CachedPointer ( CachedPointer&& other) noexcept;
 
   /// Assignment.
   CachedPointer& operator= (const CachedPointer& other);

Control/CxxUtils/CxxUtils/CachedPointer.icc

@@ -40,11 +40,23 @@ CachedPointer<T>::CachedPointer (pointer_t elt)
  */
 template <class T>
 inline
-CachedPointer<T>::CachedPointer (const CachedPointer& other)
+CachedPointer<T>::CachedPointer (const CachedPointer& other) noexcept
   : m_a (other.get())
 {
 }
 
+/**
+ * @brief Move constructor.
+ */
+template <class T>
+inline
+CachedPointer<T>::CachedPointer ( CachedPointer&& other) noexcept
+  : m_a (other.get())
+{
+   //Does not own pointer so don't need to null
+}
+
+
 
 /**
  * @brief Assignment.