Encode dir obj names before expiration (#19305)

Object names of directory objects qualified for ExpiredObjectAllVersions
must be encoded appropriately before calling on deletePrefix on their
erasure set.

e.g., a directory object and regular objects with overlapping prefixes
could lead to the expiration of regular objects, which is not the 
intention of ILM. 

```
bucket/dir/ ---> directory object
bucket/dir/obj-1
```

When `bucket/dir/` qualifies for expiration, the current implementation would
remove regular objects under the prefix `bucket/dir/`, in this case,
`bucket/dir/obj-1`.

cmd/local-locker_gen.go

@@ -21,6 +21,8 @@ func (z *localLockMap) DecodeMsg(dc *msgp.Reader) (err error) {
 			delete((*z), key)
 		}
 	}
+	var field []byte
+	_ = field
 	for zb0004 > 0 {
 		zb0004--
 		var zb0001 string
@@ -115,6 +117,8 @@ func (z *localLockMap) UnmarshalMsg(bts []byte) (o []byte, err error) {
 			delete((*z), key)
 		}
 	}
+	var field []byte
+	_ = field
 	for zb0004 > 0 {
 		var zb0001 string
 		var zb0002 []lockRequesterInfo