refactor: simplify filter plugin signatures by removing boxed parameters

src/meta_plugin/env.rs

@@ -205,7 +205,7 @@ impl MetaPlugin for EnvMetaPlugin {
     fn options(&self) -> &std::collections::HashMap<String, serde_yaml::Value> {
         use once_cell::sync::Lazy;
         static EMPTY: Lazy<std::collections::HashMap<String, serde_yaml::Value>> = 
-            Lazy::new(|| std::collections::HashMap::new());
+            Lazy::new(std::collections::HashMap::new);
         &EMPTY
     }
     
@@ -226,4 +226,4 @@ fn register_env_plugin() {
     register_meta_plugin(MetaPluginType::Env, |options, outputs| {
         Box::new(EnvMetaPlugin::new(options, outputs))
     });
-}
+}