Cherry-picking BoostToCenterOfMass and SubjetFinder changes
This cherry-picks some of the changes from https://gitlab.cern.ch/atlas/athenaprivate1/merge_requests/5552. Specifically, it moves BoostToCenterOfMass.h
to the correct directory and implements updates to SubjetFiner
. The other changes in the original MR will be cherry-picked at a later time.