Replace CxxUtils::CachedUniquePtr<const Amg::Vector3D> by Amg::Vector3D in Si/Pixel/SCT_ClusterOnTrack (ATLASRECTS-5581)

• Replace CxxUtils::CachedUniquePtr m_globalPosition by Amg::Vector3D m_globalPosition in Si/Pixel/SCT_ClusterOnTrack to avoid unnecessary memory allocation
• Set m_detEl if possible.
• No result changes are expected.
  • RunTier0Tests.py found some tiny differences mainly in electrons.
  • RunTier0Tests.log
  • diff-root-q221.AOD.log
  • diff-root-q431.AOD.log
• The differences were found to be the wrong usage of CachedUniquePtr::set in assignment operators.
  • https://its.cern.ch/jira/browse/ATLASRECTS-5581
  • This MR fixes the bug.
  • If I use CachedUniquePtr::store in assignment operators without this MR, I get results identical to results with this MR.