fix: replication metadata comparsion and other fixes (#11410)

- using miniogo.ObjectInfo.UserMetadata is not correct
- using UserTags from Map->String() can change order
- ContentType comparison needs to be removed.
- Compare both lowercase and uppercase key names.
- do not silently error out constructing PutObjectOptions
  if tag parsing fails
- avoid notification for empty object info, failed operations
  should rely on valid objInfo for notification in all
  situations
- optimize copyObject implementation, also introduce a new 
  replication event
- clone ObjectInfo() before scheduling for replication
- add additional headers for comparison
- remove strings.EqualFold comparison avoid unexpected bugs
- fix pool based proxying with multiple pools
- compare only specific metadata

Co-authored-by: Poorna Krishnamoorthy <poornas@users.noreply.github.com>

cmd/gateway/s3/gateway-s3-sse.go

@@ -365,7 +365,7 @@ func (l *s3EncObjects) GetObjectInfo(ctx context.Context, bucket string, object
 
 // CopyObject copies an object from source bucket to a destination bucket.
 func (l *s3EncObjects) CopyObject(ctx context.Context, srcBucket string, srcObject string, dstBucket string, dstObject string, srcInfo minio.ObjectInfo, s, d minio.ObjectOptions) (objInfo minio.ObjectInfo, err error) {
-	cpSrcDstSame := strings.EqualFold(path.Join(srcBucket, srcObject), path.Join(dstBucket, dstObject))
+	cpSrcDstSame := path.Join(srcBucket, srcObject) == path.Join(dstBucket, dstObject)
 	if cpSrcDstSame {
 		var gwMeta gwMetaV1
 		if s.ServerSideEncryption != nil && d.ServerSideEncryption != nil &&