Remove extern crate tracing from numerous crates.

compiler/rustc_hir/src/definitions.rs

@@ -7,15 +7,14 @@
 pub use crate::def_id::DefPathHash;
 use crate::def_id::{CrateNum, DefIndex, LocalDefId, StableCrateId, CRATE_DEF_INDEX, LOCAL_CRATE};
 use crate::def_path_hash_map::DefPathHashMap;
-
 use rustc_data_structures::stable_hasher::{Hash64, StableHasher};
 use rustc_data_structures::unord::UnordMap;
 use rustc_index::IndexVec;
 use rustc_macros::{Decodable, Encodable};
 use rustc_span::symbol::{kw, sym, Symbol};
-
 use std::fmt::{self, Write};
 use std::hash::Hash;
+use tracing::{debug, instrument};
 
 /// The `DefPathTable` maps `DefIndex`es to `DefKey`s and vice versa.
 /// Internally the `DefPathTable` holds a tree of `DefKey`s, where each `DefKey`