I realized that we'll need to make the layout interner more complicated
to support things like recursive pointers pointing to their parents and
to support lambda set layout caching. Since the layout interner is the
only user of intern crate right now anyway, just inline the whole thing.
Previously we only collected type names that appeared on the surface of
a type during alias analysis, but certain types that need to be named
(i.e. recursive types) may be observed only when we actually convert the IR
to the morphic IR. Make sure we collect those appropriately.
This is a cherry pick of the relevant changes in #4121.
