tapdb: update QueryMultiverseLeaves to return SMT leaf info

By modifying this query we can simplify other logic as now we get the
full context which includes the value+sum of the SMT leaf. In this case,
the value is the universe root hash, and the sum the root sum.

Author: Roasbeef

tapdb/sqlc/queries/universe.sql

@@ -508,8 +508,12 @@ DELETE FROM multiverse_leaves
 WHERE leaf_node_namespace = @namespace AND leaf_node_key = @leaf_node_key;
 
 -- name: QueryMultiverseLeaves :many
-SELECT r.namespace_root, r.proof_type, l.asset_id, l.group_key, l.leaf_node_key
+SELECT r.namespace_root, r.proof_type, l.asset_id, l.group_key, 
+       smt_nodes.value AS universe_root_hash, smt_nodes.sum AS universe_root_sum
 FROM multiverse_leaves l
+JOIN mssmt_nodes smt_nodes
+  ON l.leaf_node_key = smt_nodes.key AND
+     l.leaf_node_namespace = smt_nodes.namespace
 JOIN multiverse_roots r
   ON l.multiverse_root_id = r.id
 WHERE r.proof_type = @proof_type AND