Remove extern crate rustc_middle from numerous crates.

compiler/rustc_borrowck/src/diagnostics/move_errors.rs

@@ -4,6 +4,7 @@
 use rustc_errors::{Applicability, Diag};
 use rustc_hir::intravisit::Visitor;
 use rustc_hir::{CaptureBy, ExprKind, HirId, Node};
+use rustc_middle::bug;
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, Ty};
 use rustc_mir_dataflow::move_paths::{LookupResult, MovePathIndex};