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/object-capacity/src/capacity_manager.rs

@@ -1035,6 +1035,7 @@ impl HybridCapacityManager {
     ///
     /// Joiners subscribe to the watch channel *before* releasing the mutex, which guarantees
     /// they cannot miss the completion notification even if the leader finishes very quickly.
+    #[hotpath::measure]
     pub async fn refresh_or_join<F, Fut>(&self, source: DataSource, refresh_fn: F) -> Result<CapacityUpdate, String>
     where
         F: FnOnce() -> Fut,
@@ -1142,6 +1143,7 @@ impl HybridCapacityManager {
     }
 
     /// Start a background refresh if one is not already in flight.
+    #[hotpath::measure]
     pub async fn spawn_refresh_if_needed<F, Fut>(self: Arc<Self>, source: DataSource, refresh_fn: F) -> bool
     where
         F: FnOnce() -> Fut + Send + 'static,

crates/object-capacity/src/scan.rs

@@ -338,6 +338,7 @@ pub async fn select_capacity_refresh_disks(
     }
 }
 
+#[hotpath::measure]
 pub async fn refresh_capacity_with_scope(disks: Vec<CapacityDiskRef>, dirty_subset: bool) -> Result<CapacityUpdate, String> {
     let scan_started_at = Instant::now();
     let report = calculate_data_dir_used_capacity_report(&disks)