Rollup merge of #129767 - nnethercote:rm-extern-crate-tracing-4, r=jieyouxu

Remove `#[macro_use] extern crate tracing`, round 4

Because explicit importing of macros via use items is nicer (more standard and readable) than implicit importing via #[macro_use]. Continuing the work from #124511, #124914, and #125434. After this PR no `rustc_*` crates use `#[macro_use] extern crate tracing` except for `rustc_codegen_gcc` which is a special case and I will do separately.

r? ```@jieyouxu```

compiler/rustc_trait_selection/src/traits/util.rs

@@ -12,6 +12,7 @@ use rustc_middle::ty::{
 };
 use rustc_span::Span;
 use smallvec::{smallvec, SmallVec};
+use tracing::debug;
 
 use super::{NormalizeExt, ObligationCause, PredicateObligation, SelectionContext};