Parallelize new disks healing of different erasure sets (#15112)

- Always reformat all disks when a new disk is detected, this will
  ensure new uploads to be written in new fresh disks
- Always heal all buckets first when an erasure set started to be healed
- Use a lock to prevent two disks belonging to different nodes but in
  the same erasure set to be healed in parallel
- Heal different sets in parallel

Bonus:
- Avoid logging errUnformattedDisk when a new fresh disk is inserted but
  not detected by healing mechanism yet (10 seconds lag)

cmd/global-heal.go

@@ -171,6 +171,16 @@ func (er *erasureObjects) healErasureSet(ctx context.Context, buckets []string,
 	healBuckets := make([]string, len(buckets))
 	copy(healBuckets, buckets)
 
+	// Heal all buckets first in this erasure set - this is useful
+	// for new objects upload in different buckets to be successful
+	for _, bucket := range healBuckets {
+		_, err := er.HealBucket(ctx, bucket, madmin.HealOpts{ScanMode: scanMode})
+		if err != nil {
+			// Log bucket healing error if any, we shall retry again.
+			logger.LogIf(ctx, err)
+		}
+	}
+
 	var retErr error
 	// Heal all buckets with all objects
 	for _, bucket := range healBuckets {
@@ -189,7 +199,8 @@ func (er *erasureObjects) healErasureSet(ctx context.Context, buckets []string,
 		}
 		tracker.Object = ""
 		tracker.Bucket = bucket
-		// Heal current bucket
+		// Heal current bucket again in case if it is failed
+		// in the  being of erasure set healing
 		if _, err := er.HealBucket(ctx, bucket, madmin.HealOpts{
 			ScanMode: scanMode,
 		}); err != nil {