heal: Add MRF metrics to background heal API response (#12398)

This commit gathers MRF metrics from 
all nodes in a cluster and return it to the caller. This will show information about the 
number of objects in the MRF queues 
waiting to be healed.

cmd/erasure.go

@@ -39,15 +39,6 @@ import (
 // OfflineDisk represents an unavailable disk.
 var OfflineDisk StorageAPI // zero value is nil
 
-// partialOperation is a successful upload/delete of an object
-// but not written in all disks (having quorum)
-type partialOperation struct {
-	bucket    string
-	object    string
-	versionID string
-	failedSet int
-}
-
 // erasureObjects - Implements ER object layer.
 type erasureObjects struct {
 	GatewayUnsupported
@@ -78,8 +69,6 @@ type erasureObjects struct {
 	// legacy objects.
 	bpOld *bpool.BytePoolCap
 
-	mrfOpCh chan partialOperation
-
 	deletedCleanupSleeper *dynamicSleeper
 }