Aggregate 'only ancestor' libraries in their own groups

Put up a proof of concept but it creates far too many aggregates, libraries that are 'only ancestors' aren't grouped together in the library list so it keeps creating a new aggregate each time it discovers a new 'dependency type'.

Pushed another proof of concept that results in four aggregates on Umami pages.

Splits into:

libraries that are only dependencies of other libraries

libraries that are both dependencies and depended upon.

libraries that are neither dependencies nor dependended upon.

This results in four aggregates on each Umami page - on at least one page, all the aggregates changed so it is not working great.

I think this might be a dead-end and we should concentrate on handling this problem via the placeholdering issues instead (and 📌 By default, don't aggregate jquery.js Active as a quick fix.

Giving up on this one.