Completion stack overflow with module corner case

In completion.ml, in this function:

let rec get_module_defs : Scopes.Types.mod_case -> CompletionItem.t list option
  = function
  | Def defs -> Some (module_defs_to_completion_items defs)
  | Alias (_alias, resolved) ->
    Option.bind resolved ~f:(fun resolved ->
        List.find_map get_scope_info.definitions ~f:(function
            | Variable _ | Type _ -> None
            | Module m ->
              if String.(m.name = resolved) then get_module_defs m.mod_case else None))

It's possible we'll get a stack overflow from List.find_map, probably due to the recursive call to get_module_defs. I'm not sure how to reproduce this, but this deserves attention.

Likely we shouldn't compare the name directly with String.(m.name = resolved), but rather use UIDs for this.

Acceptance criteria

• Stack overflow is resolved.
• Tests added.