Structurally normalize in selection
We need to do this because of the fact that we're checking the `Ty::kind` on a type during selection, but goals passed into select are not necessarily normalized.
Right now, we're (kinda) unnecessarily normalizing the RHS of a trait upcasting goal, which is broken for different reasons (#113393). But I'm waiting for this PR to land before discussing that one.
r? `@lcnr`
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