fix: listing SSE encrypted multipart objects (#18786)

GetActualSize() was heavily relying on o.Parts()
to be non-empty to figure out if the object is multipart or not, 
However, we have many indicators of whether an object is multipart 
or not.

Blindly assuming that o.Parts == nil is not a multipart, is an 
incorrect expectation instead, multipart must be obtained via

- Stored metadata value indicating this is a multipart encrypted object.

- Rely on <meta>-actual-size metadata to get the object's actual size.
  This value is preserved for additional reasons such as these.

- ETag != 32 length

cmd/erasure-object.go

@@ -1559,7 +1559,6 @@ func (er erasureObjects) putObject(ctx context.Context, bucket string, object st
 		if errors.Is(err, errFileNotFound) {
 			return ObjectInfo{}, toObjectErr(errErasureWriteQuorum, bucket, object)
 		}
-		logger.LogOnceIf(ctx, err, "erasure-object-rename-"+bucket+"-"+object)
 		return ObjectInfo{}, toObjectErr(err, bucket, object)
 	}