Introduce ATT_PARTITIONED_TABLE in tablecmds.c

Introduce ATT_PARTITIONED_TABLE in tablecmds.c

Partitioned tables and normal tables have been relying on ATT_TABLE in
ATSimplePermissions() to produce error messages that depend on the
relation's relkind, because both relkinds currently support the same set
of ALTER TABLE subcommands.

A patch to restrict SET LOGGED/UNLOGGED for partitioned tables is under
discussion, and introducing ATT_PARTITIONED_TABLE makes subcommand
restrictions for partitioned tables easier to deal with, so let's add
one.  There is no functional change.

Author: Michael Paquier
Reviewed-by: Nathan Bossart
Discussion: https://postgr.es/m/Zt6cDnwSvnuLLnak@paquier.xyz