Ensure module attributes are applied to all top-level modules. (#1091)

Effectively revert #1089, and go back to putting `#[allow(dead_code)]`
on all modules for now, because the code in #1089 didn't work for
interfaces defined inline inside of worlds, which turn into top-level
modules in the Rust bindings.

crates/rust/src/interface.rs

@@ -445,6 +445,7 @@ macro_rules! {macro_name} {{
         let module = format!(
             "\
                 {docs}
+                #[allow(dead_code, clippy::all)]
                 pub mod {snake} {{
                     {used_static}
                     {module}