chore(io-metrics): remove the zero-consumer config module (391 lines) (#6008)

crates/io-metrics/src/config.rs was a near-copy of io-core's Backpressure/Deadlock configuration with already-drifted field names (high_watermark vs io-core's high_water_mark) and had no consumer outside the crate's own example: the canonical BackpressureConfig lives in crates/io-core/src/backpressure.rs. Delete the module, its lib.rs re-exports, and the example's unified-config section, and settle the corresponding ARCHITECTURE.md ledger line that tracked this copy's removal.

Ref rustfs/backlog#1833 (PR4).

crates/io-metrics/src/lib.rs

@@ -173,7 +173,6 @@ pub mod backpressure_metrics;
 pub mod cache_config;
 pub mod capacity_metrics;
 pub mod collector;
-pub mod config;
 pub mod deadlock_metrics;
 pub mod internode_metrics;
 pub mod io_metrics;
@@ -260,13 +259,6 @@ pub use timeout_metrics::{
     record_operation_progress, record_stalled_operation, record_timeout_event,
 };
 
-// Config exports
-pub use config::{
-    BackpressureSettings, CacheSettings, DEFAULT_BASE_BUFFER_SIZE, DEFAULT_CACHE_MAX_CAPACITY, DEFAULT_CACHE_MAX_MEMORY,
-    DEFAULT_CACHE_TTL_SECS, DEFAULT_MAX_BUFFER_SIZE, DEFAULT_MAX_CONCURRENT_READS, DEFAULT_MIN_BUFFER_SIZE,
-    DeadlockDetectionSettings, IoConfig, IoSchedulerSettings, TimeoutSettings,
-};
-
 // Re-exports for convenience
 pub use collector::MetricsCollector;
 pub use performance::PerformanceMetrics;