node/metabase: Provide API for SearchV2

There is a need to serve `ObjectService.SearchV2` RPC by the SN. In
order not to expand the structure and configuration of the node, the
best place to store metadata is metabase.

Metabases are extended with per-container object metadata buckets. For
each object, following indexes are created:
 - OID;
 - attribute->OID;
 - OID->attribute.

Integers are stored specifically to reach lexicographic comparisons
without decoding.

New `Search` method is provided: it allows to filter out container's
objects and receive specified attributes. Count is also limited, op is
paged via cursor. In other words, the method follows SearchV2 behavior
within single metabase.

Refs #3058.

Signed-off-by: Leonard Lyubich <leonard@morphbits.io>

pkg/local_object_storage/metabase/containers.go

@@ -184,6 +184,11 @@ func (db *DB) DeleteContainer(cID cid.ID) error {
 			return fmt.Errorf("link objects' bucket cleanup: %w", err)
 		}
 
+		// Metadata
+		if err = tx.DeleteBucket(metaBucketKey(cID)); err != nil && !errors.Is(err, bbolt.ErrBucketNotFound) {
+			return fmt.Errorf("metadata bucket cleanup: %w", err)
+		}
+
 		// indexes
 
 		err = tx.DeleteBucket(ownerBucketName(cID, buff))