build(toolchain): switch Rust channel to stable (#4775)

* Change Rust toolchain channel to stable

Signed-off-by: houseme <housemecn@gmail.com>

* style: apply clippy --fix and cargo fix lint suggestions

Run `cargo clippy --fix --all-targets --all-features` and
`cargo fix --lib --all-targets` across the workspace, then resolve the
remaining warnings by hand:

- collapse needless borrows in `format!` args, prefer `?` over explicit
  early returns, and use `.values()` / `.flatten()` iterator adapters
- rewrite the `Md5` scan loop via `manual_flatten` and re-indent the
  `select!` macro body (rustfmt skips macro interiors)
- annotate the intentional dead-code `Md5` inherent methods (constructed
  only by the test factory) with `#[allow(dead_code)]`

Behavior is unchanged.

Co-Authored-By: heihutu <heihutu@gmail.com>

---------

Signed-off-by: houseme <housemecn@gmail.com>
Co-authored-by: heihutu <heihutu@gmail.com>

rustfs/src/admin/handlers/pools.rs

@@ -786,7 +786,7 @@ impl Operation for StartDecommission {
         if let Some(first_idx) = pools_indices.first().copied()
             && let Some(client) = decommission_peer_target(&endpoints, first_idx, "start decommission", audit)?
         {
-            let pool_context = format!("pools {:?}", &pools_indices);
+            let pool_context = format!("pools {:?}", pools_indices);
             client
                 .start_decommission(pools_indices.clone())
                 .await
@@ -819,7 +819,7 @@ impl Operation for StartDecommission {
             validate_start_decommission_guards(decommission_running, rebalance_running)?;
 
             if !pools_indices.is_empty() {
-                let pool_context = format!("pools {:?}", &pools_indices);
+                let pool_context = format!("pools {:?}", pools_indices);
                 store
                     .decommission(ctx.clone(), pools_indices.clone())
                     .await

rustfs/src/admin/router.rs

@@ -2538,7 +2538,7 @@ where
         }
 
         let canonical_path = canonicalize_admin_path(req.uri.path());
-        let uri = format!("{}|{}", &req.method, canonical_path.as_ref());
+        let uri = format!("{}|{}", req.method, canonical_path.as_ref());
 
         if let Ok(mat) = self.router.at(&uri) {
             let op: &T = mat.value;