[#378] shard/gc: Limit the accumulated batch of objects to be deleted

Change Shard's garbage remover to interrupt iterating over the metabase
graveyard when the buffer is full to the max size (`WithRemoverBatchSize`
Shard's option).

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/local_object_storage/shard/gc.go

@@ -158,12 +158,16 @@ func (s *Shard) removeGarbage() {
 	buf := make([]*object.Address, 0, s.rmBatchSize)
 
 	// iterate over metabase graveyard and accumulate
-	// objects with GC mark
+	// objects with GC mark (no more the s.rmBatchSize objects)
 	err := s.metaBase.IterateOverGraveyard(func(g *meta.Grave) error {
 		if g.WithGCMark() {
 			buf = append(buf, g.Address())
 		}
 
+		if len(buf) == s.rmBatchSize {
+			return meta.ErrInterruptIterator
+		}
+
 		return nil
 	})
 	if err != nil {