Keep dd4hep id as is from geant4 in FT similarly to Muons

The following discussion from !1063 (merged) should be addressed:

• @gcorti started a discussion: (+2 comments)

  @zexu, to follow up this discussion the question is what does this method https://gitlab.cern.ch/lhcb/Detector/-/blob/master/Detector/FT/include/Detector/FT/DeFT.h?ref_type=heads#L200-203 returns?

  In other word is this ok in Boole as it is now?