Remove ATT_TABLE for ALTER TABLE ... ATTACH/DETACH

Remove ATT_TABLE for ALTER TABLE ... ATTACH/DETACH

Attempting these commands for a non-partitioned table would result in a
failure when creating the relation in transformPartitionCmd().  This
gives the possibility to throw an error earlier with a much better error
message, thanks to d69a3f4d70b7.

The extra test cases are from me.  Note that FINALIZE uses a different
subcommand and it had no coverage for its failure path with
non-partitioned tables.

Author: Álvaro Herrera, Michael Paquier
Reviewed-by: Nathan Bossart
Discussion: https://postgr.es/m/202409190803.tnis52adt2n5@alvherre.pgsql