Remove extern crate rustc_macros from rustc_middle.

compiler/rustc_middle/src/mir/consts.rs

@@ -1,6 +1,7 @@
 use std::fmt::{self, Debug, Display, Formatter};
 
 use rustc_hir::def_id::DefId;
+use rustc_macros::{HashStable, Lift, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable};
 use rustc_session::{config::RemapPathScopeComponents, RemapFileNameExt};
 use rustc_span::{Span, DUMMY_SP};
 use rustc_target::abi::{HasDataLayout, Size};