[PATCH] Fix trigger argument propagation to child partitions

The following patch fixes propagation of arguments to the trigger
function to child partitions both when initially creating the trigger
and when adding new partitions to a partitioned table.

The included regression test should demonstrate the problem, for clarity
repeated in slightly more readable form here:

bb=> create table parted_trig (a int) partition by list (a);
CREATE TABLE
bb=> create table parted_trig1 partition of parted_trig for values in (1);
CREATE TABLE
bb=> create or replace function trigger_notice() returns trigger as $$
bb$>   declare
bb$>     arg1 text = TG_ARGV[0];
bb$>     arg2 integer = TG_ARGV[1];
bb$>   begin
bb$>     raise notice 'trigger % on % % % for % args % %', TG_NAME, TG_TABLE_NAME, TG_WHEN, TG_OP, TG_LEVEL, arg1, arg2;
bb$>     return null;
bb$>   end;
bb$>   $$ language plpgsql;
CREATE FUNCTION
bb=> create trigger aaa after insert on parted_trig for each row execute procedure trigger_notice('text', 1);
CREATE TRIGGER
bb=> \d parted_trig
                 Tabelle »public.parted_trig«
 Spalte |   Typ   | Sortierfolge | NULL erlaubt? | Vorgabewert 
--------+---------+--------------+---------------+-------------
 a      | integer |              |               | 
Partitionsschlüssel: LIST (a)
Trigger:
    aaa AFTER INSERT ON parted_trig FOR EACH ROW EXECUTE PROCEDURE trigger_notice('text', '1')
Anzahl Partitionen: 1 (Mit \d+ alle anzeigen.)

bb=> \d parted_trig1
                 Tabelle »public.parted_trig1«
 Spalte |   Typ   | Sortierfolge | NULL erlaubt? | Vorgabewert 
--------+---------+--------------+---------------+-------------
 a      | integer |              |               | 
Partition von: parted_trig FOR VALUES IN (1)
Trigger:
    aaa AFTER INSERT ON parted_trig1 FOR EACH ROW EXECUTE PROCEDURE trigger_notice()

Fixed:

bb=> \d parted_trig1
                 Tabelle »public.parted_trig1«
 Spalte |   Typ   | Sortierfolge | NULL erlaubt? | Vorgabewert 
--------+---------+--------------+---------------+-------------
 a      | integer |              |               | 
Partition von: parted_trig FOR VALUES IN (1)
Trigger:
    aaa AFTER INSERT ON parted_trig1 FOR EACH ROW EXECUTE PROCEDURE trigger_notice('text', '1')

Patch is against 11.4, but applies to master with minor offset.

All regression test pass.