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/bucket-handlers.go

@@ -22,6 +22,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"net/textproto"
 	"net/url"
 	"path"
 	"path/filepath"
@@ -903,7 +904,7 @@ func (api objectAPIHandlers) PostPolicyBucketHandler(w http.ResponseWriter, r *h
 
 	// Extract metadata to be saved from received Form.
 	metadata := make(map[string]string)
-	err = extractMetadataFromMap(ctx, formValues, metadata)
+	err = extractMetadataFromMime(ctx, textproto.MIMEHeader(formValues), metadata)
 	if err != nil {
 		writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL, guessIsBrowserReq(r))
 		return