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/io-metrics/src/lib.rs

@@ -112,7 +112,8 @@ pub use deadlock_metrics::{
 // Lock metrics exports
 pub use lock_metrics::{
     LockMetricsSummary, record_contention_event, record_early_release, record_lock_hold_time, record_lock_optimization_enabled,
-    record_spin_attempt, record_spin_count_change,
+    record_object_lock_diag_acquire_duration, record_object_lock_diag_enabled, record_object_lock_diag_hold_duration,
+    record_object_lock_diag_slow_acquire, record_object_lock_diag_slow_hold, record_spin_attempt, record_spin_count_change,
 };
 
 pub use process_lock_metrics::{