Replace tracing with log (#2928)

* Replace tracing crate with log

It's just so much simpler to use

* Add `bacon wasm` job

* eframe: add a WebLogger for piping log events to the web console

crates/egui_demo_app/src/main.rs

@@ -15,8 +15,8 @@ fn main() -> Result<(), eframe::Error> {
         std::env::set_var("RUST_LOG", rust_log);
     }
 
-    // Log to stdout (if you run with `RUST_LOG=debug`).
-    tracing_subscriber::fmt::init();
+    // Log to stderr (if you run with `RUST_LOG=debug`).
+    env_logger::init();
 
     let options = eframe::NativeOptions {
         drag_and_drop_support: true,