Make the experimental route /metrics activable via HTTP

meilisearch-types/src/features.rs

@@ -5,6 +5,7 @@ use serde::{Deserialize, Serialize};
 pub struct RuntimeTogglableFeatures {
     pub score_details: bool,
     pub vector_store: bool,
+    pub metrics: bool,
 }
 
 #[derive(Default, Debug, Clone, Copy)]