Auto merge of #103858 - Mark-Simulacrum:bump-bootstrap, r=pietroalbini

Bump bootstrap compiler to 1.66

This PR:

- Bumps version placeholders to release
- Bumps to latest beta
- cfg-steps code

r? `@pietroalbini`

compiler/rustc_ast/src/visit.rs

@@ -251,7 +251,7 @@ pub trait Visitor<'ast>: Sized {
 macro_rules! walk_list {
     ($visitor: expr, $method: ident, $list: expr $(, $($extra_args: expr),* )?) => {
         {
-            #[cfg_attr(not(bootstrap), allow(for_loops_over_fallibles))]
+            #[allow(for_loops_over_fallibles)]
             for elem in $list {
                 $visitor.$method(elem $(, $($extra_args,)* )?)
             }