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/bucket-replication-metrics_gen.go

@@ -584,6 +584,7 @@ func (z *InQueueStats) DecodeMsg(dc *msgp.Reader) (err error) {
 // EncodeMsg implements msgp.Encodable
 func (z InQueueStats) EncodeMsg(en *msgp.Writer) (err error) {
 	// map header, size 0
+	_ = z
 	err = en.Append(0x80)
 	if err != nil {
 		return
@@ -595,6 +596,7 @@ func (z InQueueStats) EncodeMsg(en *msgp.Writer) (err error) {
 func (z InQueueStats) MarshalMsg(b []byte) (o []byte, err error) {
 	o = msgp.Require(b, z.Msgsize())
 	// map header, size 0
+	_ = z
 	o = append(o, 0x80)
 	return
 }