Fix the parameters order for TableAmRoutine.relation_copy_for_cluster()
Specify OldTable first, NewTable second as used by
table_relation_copy_for_cluster() and as implemented in
heapam_relation_copy_for_cluster().
Backpatch to PostgreSQL 12, where TableAmRoutine was introduced.
Discussion: https://postgr.es/m/ME3P282MB3166860D4911AE82F92DF7C5B63F2%40ME3P282MB3166.AUSP282.PROD.OUTLOOK.COM
Author: Japin Li Reviewed-by: Pavel Borisov
Backpatch-through: 12