Harmonise track selection cuts

In r22 the minimum number of silicon hits increased from 7 -> 8 for inside-out tracking at reco level. However the cut is at 4 hits for backtracking. In the short term, we just need to update the minimum si hit cut to 8 in this package to be consistent with the recommendations from tracking cp.

IN the longer term, we should use the official selections are provided by the InDetTrackSelectionTool. At the moment we instead use the custom TrackSelector class in this package, which manually implements the cuts. Ideally DataPrepUtilities would use the tool as well, since there is yet another parallel implementation of the cuts here as well.

Thanks @biliu for bringing this to my attention.