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/ios/event_loop.rs

@@ -85,7 +85,7 @@ impl ActiveEventLoop {
     pub(crate) fn exit(&self) {
         // https://developer.apple.com/library/archive/qa/qa1561/_index.html
         // it is not possible to quit an iOS app gracefully and programmatically
-        log::warn!("`ControlFlow::Exit` ignored on iOS");
+        tracing::warn!("`ControlFlow::Exit` ignored on iOS");
     }
 
     pub(crate) fn exiting(&self) -> bool {