Rollup merge of #144822 - Zalathar:hash-owner-nodes, r=compiler-errors

Return a struct with named fields from `hash_owner_nodes`

While looking through this code for other reasons, I noticed a nice opportunity to return a struct with named fields instead of a tuple. The first patch also introduces an early-return to flatten the rest of `hash_owner_nodes`.

There are further changes that could potentially be made here (renaming things, `Option<Hashes>` instead of optional fields), but I'm not deeply familiar with this code so I didn't want to disturb the calling code too much.

Author: samueltardieu