Rollup merge of #106012 - JakobDegen:retag-raw, r=RalfJung

Clarify that raw retags are not permitted in Mir

Not sure when this changed, but documentation and the validator needed to be updated. This also removes raw retags from custom mir.

cc rust-lang/miri#2735

r? `@RalfJung`

core/src/intrinsics/mir.rs

@@ -259,7 +259,6 @@ define!("mir_drop", fn Drop<T>(place: T, goto: BasicBlock));
 define!("mir_drop_and_replace", fn DropAndReplace<T>(place: T, value: T, goto: BasicBlock));
 define!("mir_call", fn Call<T>(place: T, goto: BasicBlock, call: T));
 define!("mir_retag", fn Retag<T>(place: T));
-define!("mir_retag_raw", fn RetagRaw<T>(place: T));
 define!("mir_move", fn Move<T>(place: T) -> T);
 define!("mir_static", fn Static<T>(s: T) -> &'static T);
 define!("mir_static_mut", fn StaticMut<T>(s: T) -> *mut T);