sanity check libs deduping

[aryairani]

Deduping libs vs tiered name resolution strategy? Make sure that the copies that would be excluded would be the ones we don’t want to choose anyway.

[mitchellwrosen]

I looked into this; it we do to include all direct deps, and only avoid loading names of indirect deps that have already been loaded elsewhere.

However, the logic seems faulty: we just count lib segments anywhere in a name. So if you have a namespace outside lib, but with a lib segment somewhere (which should be allowed, no?), we might not load those names.