Given the previous change to add implicit `Sized` bounds only if there
isn't already an explicit `Sized` bound, now the incr comp machinery
doesn't consider adding the explicit bound as being dirty, as long as
`-Zincremental-ignore-spans` is set.
The query accept arbitrary DefIds, not just owner DefIds.
The return can be an `Option` because if there are no nodes, then it doesn't matter whether it's due to NonOwner or Phantom.
Also rename the query to `opt_hir_owner_nodes`.
