Field-based Type hierarchy

[Veykril]

Sometimes I would love to know what types embed a given other type. It would be great if r-a could somehow show such a field embedding hierarchy. The lsp has a type hierarchy request model for sub and supertypes, I feel like we can maybe make use of this? https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_prepareTypeHierarchy

Alternatively of course we could also do an lsp extension here.

[lnicola]

We could also extend this idea to Deref.

[Veykril]

Deref I think could definitely be modeled via the sub and supertype requests (as well as trait hierarchies of course)