perf(ecstore): memoize bucket-incarnation fence validation under lifecycle read-lock coverage (#5782)

* perf(ecstore): memoize bucket-incarnation fence validation under lifecycle read-lock coverage

The PUT commit fence from #5648 validated the bucket incarnation with an uncached read (a distributed metadata-transaction read lock plus an EC quorum read of bucket metadata) on every PUT commit. Under 64-concurrency 4KiB PUT load this adds two quorum round-trips per PUT and the resulting lock-manager pressure produced ~1,000 client-visible 'Lock acquisition timeout' failures per 5-minute window (see rustfs/backlog#1776).

Memoize the validation per node while lifecycle read-lock coverage is continuous: bucket deletion/recreation requires the lifecycle WRITE lock, so while at least one read guard on this node has been held continuously the incarnation cannot have changed. The first fenced PUT in a coverage window performs the exact authoritative disk validation as before; overlapping PUTs reuse its result. The memo clears when the node's last guard drops or any guard observes a lost lock, so the next PUT revalidates from disk. Fence semantics are unchanged; only the redundant re-validations under continuous coverage are elided.

Also right-size the s3s footprint ratchet baselines: -1 s3_error! line from this change's error-path consolidation, and +1 s3s-importing file inherited from #5763 (crates/obs/src/telemetry/filter.rs) which landed on main without the baseline bump.

* fix(ecstore): carry the bucket fence registry through the rebalance test store

The rebalance entry test constructor landed on main after this branch was cut and needs the new field.

crates/ecstore/src/services/rebalance/entry.rs

@@ -607,6 +607,7 @@ mod tests {
             start_gate: tokio::sync::Mutex::new(()),
             pool_meta_save_gate: tokio::sync::Mutex::new(()),
             ctx: crate::runtime::instance::bootstrap_ctx(),
+            bucket_fence_registry: std::sync::Arc::default(),
         });
         let mut version = FileInfo::new("object.bin", 4, 2);
         version.name = "object.bin".to_string();

crates/ecstore/src/services/rebalance/rebalance_unit_tests.rs

@@ -2454,6 +2454,7 @@ async fn test_init_and_start_rebalance_rejects_second_start_after_gate() {
         start_gate: tokio::sync::Mutex::new(()),
         pool_meta_save_gate: tokio::sync::Mutex::new(()),
         ctx: crate::runtime::instance::bootstrap_ctx(),
+        bucket_fence_registry: std::sync::Arc::default(),
     });
 
     let err = store