graph: use UNION for isPublicNode query

In this commit we updated the IsPublicV1Node query to use UNION
instead of OR, since sqlite struggles to efficiently use
multiple indexes in a single query involving OR conditions across
different columns.

We use UNION ALL since the query doesn't care about duplicates.

sqldb/sqlc/graph.sql.go

@@ -2653,7 +2653,7 @@ const isPublicV1Node = `-- name: IsPublicV1Node :one
 SELECT EXISTS (
     SELECT 1
     FROM graph_channels c
-    JOIN graph_nodes n ON n.id = c.node_id_1 OR n.id = c.node_id_2
+    JOIN graph_nodes n ON n.id = c.node_id_1
     -- NOTE: we hard-code the version here since the clauses
     -- here that determine if a node is public is specific
     -- to the V1 gossip protocol. In V1, a node is public
@@ -2665,6 +2665,13 @@ SELECT EXISTS (
     WHERE c.version = 1
       AND c.bitcoin_1_signature IS NOT NULL
       AND n.pub_key = $1
+    UNION ALL
+    SELECT 1
+    FROM graph_channels c
+    JOIN graph_nodes n ON n.id = c.node_id_2
+    WHERE c.version = 1
+      AND c.bitcoin_1_signature IS NOT NULL
+      AND n.pub_key = $1
 )
 `