Implementation of DeMagnet in LHCb
This MR provides DeMagnet, a replacement for the MagneticfFieldSvc in LHCb. In the DD4hep case, the DeMagnet from the Detector project is used, for the DetDesc case the MagneticFieldSvc creates a DerivedCOndition that is a facade for the service.
Tests have been added to Det/Magnet to be able to validate the replacement.
Edited by Ben Couturier