Refactor replication resync to be an active process (#14266)

When resync is triggered, walk the bucket namespace and
resync objects that are unreplicated. This PR also adds
an API to report resync progress.

cmd/bucket-metadata.go

@@ -375,6 +375,7 @@ func deleteBucketMetadata(ctx context.Context, obj objectDeleter, bucket string)
 	metadataFiles := []string{
 		dataUsageCacheName,
 		bucketMetadataFile,
+		path.Join(replicationDir, resyncFileName),
 	}
 	for _, metaFile := range metadataFiles {
 		configFile := path.Join(bucketMetaPrefix, bucket, metaFile)