Draft: Fix offsets for unordered inserts in MultiIndexed(Hit)Container

The multi indexed container currently has some undefined behaviour in case someone adds hits 1-by-1 in an unordered manner. As there is also no sort() functionality present, one effectively either has to order the data beforehand.

This MR fixes the insert function to properly update the offsets also for the next unique detector elements.

I expect the impact to be quite minimal, as this function was only used for the v4 FT decoding and my own cluster manipulation algorithms. This is a required fix for the smaller cluster containers I want to work with.

Now part of Moore!2754 (comment 7631946) because this small MR didn't get merged..