Add self-healing feature (#7604)

- Background Heal routine receives heal requests from a channel, either to
heal format, buckets or objects
- Daily sweeper lists all objects in all buckets, these objects
don't necessarly have read quorum so they can be removed if
these objects are unhealable
- Heal daily ops receives objects from the daily sweeper
and send them to the heal routine.

cmd/fs-v1.go

@@ -1151,6 +1151,12 @@ func (fs *FSObjects) ListBucketsHeal(ctx context.Context) ([]BucketInfo, error)
 	return []BucketInfo{}, NotImplemented{}
 }
 
+// ListObjectsHeal - list all objects to be healed. Valid only for XL
+func (fs *FSObjects) ListObjectsHeal(ctx context.Context, bucket, prefix, marker, delimiter string, maxKeys int) (result ListObjectsInfo, err error) {
+	logger.LogIf(ctx, NotImplemented{})
+	return ListObjectsInfo{}, NotImplemented{}
+}
+
 // SetBucketPolicy sets policy on bucket
 func (fs *FSObjects) SetBucketPolicy(ctx context.Context, bucket string, policy *policy.Policy) error {
 	return savePolicyConfig(ctx, fs, bucket, policy)