[#1262] metabase: Optimize decodeList

Prevent additional allocation during `append` in `Put`.

```
name              old alloc/op   new alloc/op   delta
Put/parallel-8       131kB ± 1%     126kB ± 4%  -3.87%  (p=0.005 n=8+8)
Put/sequential-8     172kB ± 1%     171kB ± 1%  -0.73%  (p=0.028 n=10+9)
```

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

pkg/local_object_storage/metabase/put.go

@@ -379,7 +379,7 @@ func decodeList(data []byte) (lst [][]byte, err error) {
 	}
 	r := io.NewBinReaderFromBuf(data)
 	l := r.ReadVarUint()
-	lst = make([][]byte, l)
+	lst = make([][]byte, l, l+1)
 	for i := range lst {
 		lst[i] = r.ReadVarBytes()
 	}