refactor(data-usage): ReplicationStats -> ReplicationTargetUsage

Rename the data-usage crate's ReplicationStats to ReplicationTargetUsage.
Serde field names are byte-identical (only the Rust type name changed;
field identifiers that rmp encodes are untouched). An rmp round-trip test
guards against future drift.

Scanner test imports updated to match.

crates/scanner/src/data_usage_define/tests.rs

@@ -16,7 +16,7 @@ use super::persistence::DataUsageCacheLoadAttempt;
 use super::*;
 use crate::storage_api::scanner_io::{HTTPRangeSpec, ObjectIO};
 use crate::{ScannerGetObjectReader, ScannerPutObjReader};
-use rustfs_data_usage::{ReplicationAllStats, ReplicationStats};
+use rustfs_data_usage::{ReplicationAllStats, ReplicationTargetUsage};
 use serde_json::Value;
 use std::io::Cursor;
 use std::pin::Pin;
@@ -1636,7 +1636,7 @@ fn size_recursive_prunes_empty_and_preserves_threshold_replication_stats() {
             replication_stats: Some(ReplicationAllStats {
                 targets: HashMap::from([(
                     "arn:test:threshold".to_string(),
-                    ReplicationStats {
+                    ReplicationTargetUsage {
                         after_threshold_count: 1,
                         ..Default::default()
                     },

crates/scanner/src/scanner_io/publish_gate_tests.rs

@@ -13,7 +13,7 @@
 // limitations under the License.
 
 use super::*;
-use rustfs_data_usage::{ReplicationAllStats, ReplicationStats};
+use rustfs_data_usage::{ReplicationAllStats, ReplicationTargetUsage};
 
 const TEST_PLAN_DIGEST: DataUsageScanPlanDigest = DataUsageScanPlanDigest([7; 32]);
 
@@ -271,7 +271,7 @@ fn completed_data_usage_info_flattens_nested_bucket_entries() {
         replication_stats: Some(ReplicationAllStats {
             targets: HashMap::from([(
                 "arn:target".to_string(),
-                ReplicationStats {
+                ReplicationTargetUsage {
                     replicated_size: 2048,
                     replicated_count: 2,
                     ..Default::default()