Replace log with tracing

Tracing is a modern replacement for the log crate that allows for
annotating log messages with the function that they come from.

Signed-off-by: John Nunley <dev@notgull.net>
Closes: #3482

src/platform_impl/orbital/event_loop.rs

@@ -537,7 +537,7 @@ impl<T: 'static> EventLoop<T> {
                 }
             }
             other => {
-                log::warn!("unhandled event: {:?}", other);
+                tracing::warn!("unhandled event: {:?}", other);
             }
         }
     }