Remove extern crate rustc_middle from numerous crates.

compiler/rustc_mir_dataflow/src/framework/engine.rs

@@ -13,6 +13,7 @@ use rustc_data_structures::work_queue::WorkQueue;
 use rustc_graphviz as dot;
 use rustc_hir::def_id::DefId;
 use rustc_index::{Idx, IndexVec};
+use rustc_middle::bug;
 use rustc_middle::mir::{self, traversal, BasicBlock};
 use rustc_middle::mir::{create_dump_file, dump_enabled};
 use rustc_middle::ty::print::with_no_trimmed_paths;