Auto merge of rust-lang#115025 - ouz-a:ouz_testing, r=lcnr

Make subtyping explicit in MIR

This adds new mir-opt that pushes new `ProjectionElem` called `ProjectionElem::Subtype(T)` to `Rvalue` of a subtyped assignment so we can unsoundness issues like rust-lang#107205

Addresses rust-lang#112651

r? `@lcnr`

clippy_utils/src/qualify_min_const_fn.rs

@@ -272,6 +272,7 @@ fn check_place<'tcx>(tcx: TyCtxt<'tcx>, place: Place<'tcx>, span: Span, body: &B
             | ProjectionElem::Downcast(..)
             | ProjectionElem::Subslice { .. }
             | ProjectionElem::Deref
+            | ProjectionElem::Subtype(_)
             | ProjectionElem::Index(_) => {},
         }
     }