fix(ecstore): split internal get metadata metrics (#5687)

Classify expected metadata-missing errors separately from unknown get pipeline failures and attribute internal meta-bucket reader failures to an internal_meta path instead of legacy_duplex.

This keeps scanner/data-usage metadata probes from polluting user GET/mixed failure attribution while preserving the existing read error behavior.

Co-authored-by: heihutu <heihutu@gmail.com>

rustfs/src/lib.rs

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#![recursion_limit = "256"]
+
 //! RustFS — high-performance S3-compatible object storage.
 //!
 //! This library exposes the [`embedded`] module which lets you start a