Structural resolve doesn't actually structurally resolve

[compiler-errors]

struct Foo {
    value: usize,
}

fn foo(t: [Foo; 1]) -> usize {
    t[0].value
}

error[E0609]: no field `value` on type `<usize as SliceIndex<[Foo]>>::Output`
 --> <source>:6:10
  |
6 |     t[0].value
  |

We need to normalize any projections eagerly within structurally_resolve, or at least ones that show up at the root of the type (i.e. no need to normalize the projection in Wrapper<<Ty as Trait>::Assoc>.

The fix is rougly compiler-errors/rust@6edd004.