We no longer test with ROOT 6.22, and in 6.32 PyROOT is coming back but subtly fails on macOS

Avoid having another level of quotes or b'' showing up in the wrong places

Typename: do not inherit from std::pair because ROOT stopped working for this construct for some reason

when the value is used as 'half-length'
replacing GetNegativeEndZ by GetPositiveEndZ fixes the problem
because GetPositiveEndZ is the user value that corresponds to half-length

LCIO now exports LCIO::lcio, so we could use that if LCIO is new enough

Explicity set namespace to TrackClassification in
TestStackingAction::classifyNewTrack

Co-authored-by: Andre Sailer <andre.philippe.sailer@cern.ch>

Co-authored-by: Andre Sailer <andre.philippe.sailer@cern.ch>

Co-authored-by: Andre Sailer <andre.philippe.sailer@cern.ch>

Remove support for very old versions of ROOT < 6.26.0. Remove default use of std namespace from some implementation files.