We have a way to find the children of a CHAINED collection, but no good way to do the reverse.
Add unlink option to butler remove-runs
Registry.getCollectionParentChains isn't reliable
Simple change, except for all of the layers of interface it has to get passed through. Most obvious use is on DM-33619, but it might be a nice thing to try to incorporate into the query-collections CLI, too.
Looks okay to me.