Consider exposing topology differences

[HadrienG2]

Expose hwloc's ability to compute diffs of topologies that are similar but not quite identical: https://hwloc.readthedocs.io/en/v2.9/group__hwlocality__diff.html

[HadrienG2]

I must admit that the use case for this (topology diff that only works in simple cases and errors out otherwise) is a bit unclear to me at the moment. That makes it hard to find motivation for binding it and inspiration for API ergonomics. If you use or would want to use this feature, please speak up and describe your use case!