Updated BeamPipeBuilder to pick physical radius

This MR updates the way the beam pipe radius is retrieved to build the InDetTrackingGeometry, based on the observation in Phase 2 studies that it is wrongly set at 27mm in tracking material map, instead of the expected 24mm. This is believed to be due to the fact that the radius retrieved is the one of the logical volume associated to the beam pipe which does not correspond to the physical volume. This updates returns the expected 24mm and it was checked to have a minimal impact when used together with the existing tracking material maps of ATLAS-P2-ITK-22-02-00.

FYI: @ncalace @nstyles @goblirsc @npetters