AthContainersInterfaces,etc: Change getSelectedAuxIDs to return by value.

Control/AthContainers/test/copyAuxStoreThinned_test.cxx

...ontainersInterfaces/AthContainersInterfaces/IAuxStoreIO.h

Control/xAODRootAccess/Root/TAuxStore.cxx

Control/xAODRootAccess/Root/TEvent.cxx

Control/xAODRootAccess/xAODRootAccess/TAuxStore.h

Database/AthenaPOOL/AthenaPoolCnvSvc/src/AuxDiscoverySvc.cxx

Database/AthenaPOOL/AthenaPoolCnvSvc/src/AuxDiscoverySvc.h

Event/xAOD/xAODCore/Root/AuxContainerBase.cxx

Event/xAOD/xAODCore/Root/AuxInfoBase.cxx

Event/xAOD/xAODCore/Root/AuxSelection.cxx

Event/xAOD/xAODCore/Root/ShallowAuxContainer.cxx

Event/xAOD/xAODCore/xAODCore/AuxContainerBase.h

Event/xAOD/xAODCore/xAODCore/AuxInfoBase.h

Event/xAOD/xAODCore/xAODCore/AuxSelection.h

Event/xAOD/xAODCore/xAODCore/ShallowAuxContainer.h

Trigger/TrigEvent/TrigNavigation/src/Holder.cxx