misc: tracer: drop extern crate, use modern rust

This commit is part of a series of similar commits.

Signed-off-by: Philipp Schuster <philipp.schuster@cyberus-technology.de>
On-behalf-of: SAP philipp.schuster@sap.com

tracer/src/lib.rs

@@ -3,10 +3,6 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 
-#[cfg(feature = "tracing")]
-#[macro_use]
-extern crate log;
-
 #[cfg(not(feature = "tracing"))]
 mod tracer_noop;
 #[cfg(not(feature = "tracing"))]

tracer/src/tracer.rs

@@ -13,6 +13,7 @@ use std::sync::atomic::{AtomicU64, Ordering};
 use std::sync::{Arc, Mutex};
 use std::time::{Duration, Instant};
 
+use log::warn;
 use serde::Serialize;
 
 #[derive(Debug)]