Rollup merge of #119817 - compiler-errors:normalize-opaques, r=lcnr

Remove special-casing around `AliasKind::Opaque` when structurally resolving in new solver

This fixes a few inconsistencies around where we don't eagerly resolve opaques to their (locally-defined) hidden types in the new solver. It essentially allows this code to work:
```rust
fn main() {
    type Tait = impl Sized;
    struct S {
        i: i32,
    }
    let x: Tait = S { i: 0 };
    println!("{}", x.i);
}
```

Since `Tait` is defined in `main`, we are able to poke through the type of `x` with deref.

r? lcnr

compiler/rustc_hir_analysis/src/autoderef.rs

@@ -74,7 +74,7 @@ impl<'a, 'tcx> Iterator for Autoderef<'a, 'tcx> {
             // we have some type like `&<Ty as Trait>::Assoc`, since users of
             // autoderef expect this type to have been structurally normalized.
             if self.infcx.next_trait_solver()
-                && let ty::Alias(ty::Projection | ty::Inherent | ty::Weak, _) = ty.kind()
+                && let ty::Alias(..) = ty.kind()
             {
                 let (normalized_ty, obligations) = self.structurally_normalize(ty)?;
                 self.state.obligations.extend(obligations);