Rollup merge of #83916 - Amanieu:asm_anonconst, r=petrochenkov

Use AnonConst for asm! constants

This replaces the old system which used explicit promotion. See #83169 for more background.

The syntax for `const` operands is still the same as before: `const <expr>`.

Fixes #83169

Because the implementation is heavily based on inline consts, we suffer from the same issues:
- We lose the ability to use expressions derived from generics. See the deleted tests in `src/test/ui/asm/const.rs`.
- We are hitting the same ICEs as inline consts, for example #78174. It is unlikely that we will be able to stabilize this before inline consts are stabilized.

clippy_utils/src/hir_utils.rs

@@ -663,7 +663,8 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
                                 self.hash_expr(out_expr);
                             }
                         },
-                        InlineAsmOperand::Const { expr } | InlineAsmOperand::Sym { expr } => self.hash_expr(expr),
+                        InlineAsmOperand::Const { anon_const } => self.hash_body(anon_const.body),
+                        InlineAsmOperand::Sym { expr } => self.hash_expr(expr),
                     }
                 }
             },