[PATCH] Add pretty formatting to pg_get_triggerdef

Hello Hackers,

Currently, `pg_get_triggerdef` includes a "pretty" flag, but it does not
actually format the `CREATE TRIGGER` statement in a "pretty" way. Unlike
`pg_get_viewdef`, `pg_get_ruledef`, and `pg_get_indexdef`, the purpose of
pretty formatting has been to remove the schema name so it can be used by
the `\d` psql comment to display triggers associated with a view or table,
as shown below:

postgres=# \d main_table
Table "public.main_table"
Column | Type | Collation | Nullable | Default
--------+---------+-----------+----------+---------
a | integer | | |
b | integer | | |
Indexes:
"main_table_a_key" UNIQUE CONSTRAINT, btree (a)
Triggers:
foofoo AFTER INSERT ON main_table FOR EACH STATEMENT EXECUTE FUNCTION
trigger_func('foo_bar')
foo_bar BEFORE INSERT ON main_table FOR EACH STATEMENT EXECUTE FUNCTION
trigger_func('foo_bar')
bar_fooAFTER DELETE ON main_table FOR EACH ROW WHEN ((old.a = 123))
EXECUTE FUNCTION trigger_func('foo_bar')

This patch introduces true pretty formatting to `pg_get_triggerdef`.
Additionally, it creates a new function specifically for the `\d` psql
command, as that command requires schema removal and a single line
statement.

With this patch, when the `pretty` parameter is set to `true`,
`pg_get_triggerdef` now displays a formatted output, consistent with
`pg_get_viewdef`, `pg_get_ruledef`, and `pg_get_indexdef`:

postgres=# select pg_get_triggerdef(12345, true);
pg_get_triggerdef
--------------------------------------------------
CREATE TRIGGER some_trig_foobar AFTER UPDATE +
ON some_t +
FOR EACH ROW +
WHEN (NOT new.some_col) +
EXECUTE FUNCTION dummy_update_func('foobar')
(1 row)

When the `pretty` flag is `false`, the function's behavior remains
unchanged from the original implementation:

postgres=# select pg_get_triggerdef(47901, false);

pg_get_triggerdef

---------------------------------------------------------------------------------------------------------------------------------------------------
CREATE TRIGGER some_trig_foobar AFTER UPDATE ON public.some_t FOR EACH ROW
WHEN ((NOT new.some_col)) EXECUTE FUNCTION dummy_update_func('foobar')
(1 row)

--
Best,
Phil Alger