Introduce key-id renumber helper module
When doing wild splitting, resizing and merging, we join multiple keystreams from different sources.
The key-ids inside each stream may be unique but not disjunct when combined. Therefore we have to have some utility module which enforces a key renumbering. Much like https://sqt.ait.ac.at/software/projects/qkd/wiki/Core-Modules#qkd-sifting-bb84.
This could be a feature of every module. So on output, each module might renumber the key according to these settings.