[#176] localstore: Implement shard methods via Metabase and BlobStor

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

pkg/local_object_storage/metabase/exists.go

@@ -0,0 +1,21 @@
+package meta
+
+import (
+	"github.com/nspcc-dev/neofs-api-go/pkg/object"
+	"github.com/pkg/errors"
+)
+
+// Exists checks if object is presented in metabase.
+func (db *DB) Exists(addr *object.Address) (bool, error) {
+	// FIXME: temp solution, avoid direct Get usage
+	_, err := db.Get(addr)
+	if err != nil {
+		if errors.Is(err, errNotFound) {
+			return false, nil
+		}
+
+		return false, err
+	}
+
+	return true, nil
+}