Atomically create table and its partitions

This is to avoid a race condition when we succeed to create the
partitioned table but failed to create its partitions.

In that case, automatic partition management might kick in leading to
undesired states.

We basically want the migration to fully succeed first, before
partitions are being automatically managed.

Relates to https://gitlab.com/gitlab-org/omnibus-gitlab/-/issues/5597

lib/gitlab/database/partitioning_migration_helpers/table_management_helpers.rb

@@ -62,8 +62,10 @@ module Gitlab
 
           partitioned_table_name = make_partitioned_table_name(table_name)
 
-          create_range_partitioned_copy(table_name, partitioned_table_name, partition_column, primary_key)
-          create_daterange_partitions(partitioned_table_name, partition_column.name, min_date, max_date)
+          transaction do
+            create_range_partitioned_copy(table_name, partitioned_table_name, partition_column, primary_key)
+            create_daterange_partitions(partitioned_table_name, partition_column.name, min_date, max_date)
+          end
           create_trigger_to_sync_tables(table_name, partitioned_table_name, primary_key)
         end