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/object-api-datatypes.go

@@ -244,6 +244,51 @@ type ObjectInfo struct {
 	SuccessorModTime time.Time
 }
 
+// Clone - Returns a cloned copy of current objectInfo
+func (o ObjectInfo) Clone() (cinfo ObjectInfo) {
+	cinfo = ObjectInfo{
+		Bucket:             o.Bucket,
+		Name:               o.Name,
+		ModTime:            o.ModTime,
+		Size:               o.Size,
+		IsDir:              o.IsDir,
+		ETag:               o.ETag,
+		InnerETag:          o.InnerETag,
+		VersionID:          o.VersionID,
+		IsLatest:           o.IsLatest,
+		DeleteMarker:       o.DeleteMarker,
+		TransitionStatus:   o.TransitionStatus,
+		RestoreExpires:     o.RestoreExpires,
+		RestoreOngoing:     o.RestoreOngoing,
+		ContentType:        o.ContentType,
+		ContentEncoding:    o.ContentEncoding,
+		Expires:            o.Expires,
+		CacheStatus:        o.CacheStatus,
+		CacheLookupStatus:  o.CacheLookupStatus,
+		StorageClass:       o.StorageClass,
+		ReplicationStatus:  o.ReplicationStatus,
+		UserTags:           o.UserTags,
+		Parts:              o.Parts,
+		Writer:             o.Writer,
+		Reader:             o.Reader,
+		PutObjReader:       o.PutObjReader,
+		metadataOnly:       o.metadataOnly,
+		versionOnly:        o.versionOnly,
+		keyRotation:        o.keyRotation,
+		backendType:        o.backendType,
+		AccTime:            o.AccTime,
+		Legacy:             o.Legacy,
+		VersionPurgeStatus: o.VersionPurgeStatus,
+		NumVersions:        o.NumVersions,
+		SuccessorModTime:   o.SuccessorModTime,
+	}
+	cinfo.UserDefined = make(map[string]string, len(o.UserDefined))
+	for k, v := range o.UserDefined {
+		cinfo.UserDefined[k] = v
+	}
+	return cinfo
+}
+
 // MultipartInfo captures metadata information about the uploadId
 // this data structure is used primarily for some internal purposes
 // for verifying upload type such as was the upload