After changing the handling of exterior/unlabeled labels (no explicit label instance any more), some tool do not work properly any more.

Can be seen e.g. with the Otsu tool.

1. The result 0 cannot be selected anymore or transfered. Reason currently 0 (unlabeledValue) is always ignored. => we have to see if we let tools decide if they want to ignore 0. But for those who want not, the whole result must be shiftet (e.g. with transferLabelContent).
2. If you have already a label with content. The content seems not to be overwritten, even if it should. Also if (e.g. in Otsu you first previewed with n (e.g. 4) regions and then reduce to n-1 regions. Still n labels are there, because the current transfer does no "removing" update. -> Revise the whole tranfer label and update preview strategy. Also needed for tools like nnUnet and TotalSegmentator

Look into that issue together with T29451