Move `Resolver` fields specific to late resolution to the new visitor.
The `current_module` field from `Resolver` is replaced with two `current_module`s in `LateResolutionVisitor` and `BuildReducedGraphVisitor`.
Outside of those visitors `current_module` is replaced by passing `parent_scope` to more functions and using the parent module from it.
Visibility resolution no longer have access to later resolution methods and has to use early resolution, so its diagnostics in case of errors regress slightly.
