035_standby_logical_decoding: Add missing waits for replication

At least one slow buildfarm system (hoverfly) showed that the database
creation was not replicated before we try to create logical replication slots
on the standby, in that database.

Reported-by: Noah Misch <noah@leadboat.com>
Author: "Drouvot, Bertrand" <bertranddrouvot.pg@gmail.com>
Discussion: https://postgr.es/m/20230411053657.GA1177147@rfd.leadboat.com

Author: anarazel

src/test/recovery/t/035_standby_logical_decoding.pl

@@ -653,9 +653,15 @@ sub check_for_invalidation
 $node_primary->psql('postgres', q[CREATE DATABASE testdb]);
 $node_primary->safe_psql('testdb', qq[CREATE TABLE decoding_test(x integer, y text);]);
 
+# Wait for the standby to catchup before creating the slots
+$node_primary->wait_for_replay_catchup($node_standby);
+
 # create the logical slots
 create_logical_slots($node_standby, 'promotion_');
 
+# Wait for the cascading standby to catchup before creating the slots
+$node_standby->wait_for_replay_catchup($node_cascading_standby, $node_primary);
+
 # create the logical slots on the cascading standby too
 create_logical_slots($node_cascading_standby, 'promotion_');