Allow for sensitive actions with multiple readout segmentation in the Geant4Sensitive action sequence

Allow for sensitive actions with multiple readout segmentation in the Geant4Sensitive action sequence

Allow for sensitive actions with multiple readout segmentation in the Geant4Sensitive action sequence

Allow for sensitive actions with multiple readout segmentation in the Geant4Sensitive action sequence

Allow for sensitive actions with multiple readout segmentation in the Geant4Sensitive action sequence

Allow for sensitive actions with multiple readout segmentation in the Geant4Sensitive action sequence

Allow for sensitive actions with multiple readout segmentation in the Geant4Sensitive action sequence

Allow for sensitive actions with multiple readout segmentation in the Geant4Sensitive action sequence

Allow for sensitive actions with multiple readout segmentation in the Geant4Sensitive action sequence

Allow for sensitive actions with multiple readout segmentation in the Geant4Sensitive action sequence

This allows syntax like
```xml
  <detectors>
    <detector id="1" name="FT_MT" type="DD4hep_GdmlDetector" vis="InvisibleWithChildren">
      <gdmlFile ref="GdmlDetector.gdml" physvol="lvUpstreamRegion_0"/>
      <parent name="/world"/>
    </detector>
  </detectors>
```
to only load the specific `physvol` in `examples/ClientTests/compact/GdmlDetector.gdml`.

Co-authored-by: Andre Sailer <andre.philippe.sailer@cern.ch>