Support overlaping segments from SEG dicom file

 Approach: make a new segment group for each component output from  `@itk-wasm/dicom::readOverlappingSegments`.  Could be very simple by just looping code here: https://github.com/Kitware/VolView/blob/main/src/store/segmentGroups.ts#L253-L294
