Rollup merge of #82091 - henryboisdequin:use-place-ref-more, r=RalfJung

use PlaceRef abstractions more consistently

Addresses this [comment](https://github.com/rust-lang/rust/pull/80865/files#r558978715)
Associated issue: #80647

r? ```@RalfJung```

compiler/rustc_mir/src/transform/simplify.rs

@@ -413,8 +413,7 @@ impl UsedLocals {
         } else {
             // A definition. Although, it still might use other locals for indexing.
             self.super_projection(
-                place.local,
-                &place.projection,
+                place.as_ref(),
                 PlaceContext::MutatingUse(MutatingUseContext::Projection),
                 location,
             );