feat: extend hotpath coverage across crates (#5505)

Add opt-in hotpath feature surfaces to every workspace crate and wire the root rustfs feature passthrough for function, allocation, and CPU profiling.

Add a focused set of function-level measurements for scanner, heal, lock, target replay, IAM, KMS, Keystone, trusted proxy, and capacity paths without adding request-scoped primitive wrappers.

Co-authored-by: heihutu <heihutu@gmail.com>

crates/iam/src/store/object.rs

@@ -469,6 +469,7 @@ impl ObjectStore {
         });
     }
 
+    #[hotpath::measure]
     async fn list_all_iamconfig_items(&self) -> Result<HashMap<String, Vec<String>>> {
         let (tx, mut rx) = mpsc::channel::<StringOrErr>(100);
 
@@ -508,6 +509,7 @@ impl ObjectStore {
         Ok(res)
     }
 
+    #[hotpath::measure]
     async fn load_policy_doc_concurrent(&self, names: &[String], mode: LoadMode) -> Result<Vec<PolicyDoc>> {
         let mut futures = Vec::with_capacity(names.len());