refactor: improve logs, unify integration log fmt

The catch-all case of `handle_client_message` now logs the atom's name
instead of its opaque atom id.

`get_atom_name` now warns there was an error and returns a filler name.
Since most the use of `get_atom_name` is in logging, this makes those
logs easier to read.

The integration tests now use `formatted_timed_builder` logger
constructor, which should unify the look of logs between the integration
tests and the main binary.

tests/integration.rs

@@ -126,7 +126,7 @@ impl Fixture {
     fn new_preset(pre_connect: impl FnOnce(&mut testwl::Server)) -> Self {
         static INIT: Once = Once::new();
         INIT.call_once(|| {
-            pretty_env_logger::env_logger::builder()
+            pretty_env_logger::formatted_timed_builder()
                 .is_test(true)
                 .filter_level(log::LevelFilter::Debug)
                 .parse_default_env()