normalize in `trait_ref_is_knowable` in new solver
fixes https://github.com/rust-lang/trait-system-refactor-initiative/issues/51
Alternatively we could avoid normalizing the self type and do this at the end of the `assemble_candidates_via_self_ty` stack by splitting candidates into:
- applicable without normalizing self type
- applicable for aliases, even if they can be normalized
- applicable for stuff which cannot get normalized further
I don't think this would have any significant benefits and it also seems non-trivial to avoid normalizing only the self type in `trait_ref_is_knowable`.
r? `@compiler-errors`
7455aa5395