jet hypo: ensure the jet groups do not acquire duplicates + minor changes
When leaf nodes of a FastReduction Condition tree includes Conditions with capacity > 1, the checks made so far to ensure the absence of duplicates in jet groups are insufficient Add further checks.
This is an edge case: we have no such chains, and may never have, but they are in principle configurable, hence the checks are needed.
The merge requests include some small changes to the combinatoric generator interface, and implementations, plus a new ctest.