moved LineTraj to Detector package
This is needed at least in FT and UT interfaces when moving them to DD4hep
Part of the following set of MRs : !110 (merged) LHCb!3294 (merged) Rec!2594 (merged) Phys!1003 (merged) Boole!363 (merged) Run2Support!18 (merged)
Edited by Sebastien Ponce