Apply r21 changes of tau physics validation to master
A bunch of merge commits in r21 were not swept to master. Here, I've cherry-picked the merge commits to get master up to-date with r21. I also changed the TauSelectionTool and TauTruthMatchingTools used in PhysValTau to ToolHandles.
A small fix to TauSelectionTool had to be implemented as discussed in ATLTAU-1646.
I've successfully checked the tau NTUP_PHYSVAL and it looks good. I also successfully ran the Tier 0: RunTier0Tests.log
Edited by Mikael Martensson