Minor updates and Rich2 Detector element examples

patch generated by https://gitlab.cern.ch/lhcb/Detector/-/jobs/18616823 This has minor geometry overlap fixes, some updates for Gaussino usage, introduction of Rich2 detector element access classes and some file reorganization.

assigned to @bcouturi

approved this merge request

added lhcb-dd4hep label

• [2022-01-11 11:48] Validation started with lhcb-dd4hep#1015
• [2022-01-11 13:04] Validation started with lhcb-dd4hep#1016

mentioned in merge request !140 (merged)

removed lhcb-dd4hep label

closed