Add move special members, member-swap, Q_DECLARE_SHARED for all value classes

Adding Q_DECLARE_SHARED includes, in particular, Q_DECLARE_TYPEINFO(., Q_RELOCATABLE_TYPE), the addition of which is BiC, because the memory layout of QVariant changes for relocatable types. So it must be done before 6.3.0, sorry. At least the Q_DECLARE_SHARED and therefore member-swap. I don't think Q_D_S checks move special member functions, so that can wait.