feat(ecstore): add object lock diagnostics (#3178)

* feat(ecstore): add object lock diagnostics

Add configurable namespace lock diagnostics for object operations so production contention can be traced by operation, owner, and key.

Wrap object read/write lock acquisition in diagnostic guards across get, head, put, delete, copy, and multipart flows, and log slow acquisition and long hold durations behind new RUSTFS_OBJECT_LOCK_DIAG_* settings.

Verification:

- make pre-commit

* feat(obs): expose object lock diagnostics metrics

Add Prometheus metrics and Grafana panels for object namespace lock diagnostics, covering slow acquire counts, slow hold counts, acquire duration, hold duration, and the diagnostics-enabled state.

Adopt PR review feedback by keeping diagnostic guards alive through the guarded operation so long-hold warnings and metrics are emitted, reusing shared env helpers, and reducing default-path overhead when diagnostics are disabled.

Verification:

- cargo check -p rustfs-ecstore -p rustfs-io-metrics

- cargo test -p rustfs-ecstore store::object -- --nocapture

- make pre-commit

* perf(obs): reduce object lock diag overhead

Avoid repeated environment parsing on hot object-lock paths by caching the diagnostics-enabled flag, and stop allocating label strings for object lock metrics by recording static labels directly.

Strengthen io-metrics tests by using a local recorder and asserting that the expected object lock diagnostic counters, gauges, and histograms are emitted.

Verification:

- cargo check -p rustfs-ecstore -p rustfs-io-metrics

- cargo test -p rustfs-io-metrics -- --nocapture

- make pre-commit

crates/lock/src/namespace/mod.rs

@@ -52,6 +52,11 @@ impl NamespaceLockWrapper {
         Self { lock, resource, owner }
     }
 
+    /// Get lock owner identifier used for acquisition.
+    pub fn owner(&self) -> &str {
+        &self.owner
+    }
+
     /// Acquire write lock (exclusive lock) with timeout
     /// Returns the guard if acquisition succeeds, or an error if it fails
     pub async fn get_write_lock(&self, timeout: Duration) -> std::result::Result<NamespaceLockGuard, crate::error::LockError> {