Remove use of session_preload_libraries in regression tests

session_preload_libraries was not really required with its set of ALTER
DATABASE SET commands to updates some GUCs.  There were equivalent LOAD
and SET commands used in the tests where session_preload_libraries was
defined, and the same GUCs were set twice.

This simplifies the tests, while shaving some cycles to run the tests.

Backpatch-through: 17

expected/ut-G.out

@@ -675,7 +675,6 @@ error hint:
                Filter: ((ctid = '(1,1)'::tid) AND (c1 = 1))
 (65 rows)
 
-RESET client_min_messages;
 ----
 ---- No. G-2-1 GUC parameter
 ----

expected/ut-S.out

@@ -1,11 +1,4 @@
 LOAD 'pg_hint_plan';
--- Force some GUCs.
-SELECT current_database() AS datname \gset
-ALTER DATABASE :"datname" SET client_min_messages = 'log';
-ALTER DATABASE :"datname" SET pg_hint_plan.debug_print = 'on';
-ALTER DATABASE :"datname" SET session_preload_libraries TO 'pg_hint_plan';
--- Force GUC reload with a reconnection
-\c
 SET pg_hint_plan.enable_hint TO on;
 SET pg_hint_plan.debug_print TO on;
 SET client_min_messages TO LOG;

expected/ut-W.out

@@ -1,5 +1,4 @@
 LOAD 'pg_hint_plan';
-ALTER SYSTEM SET session_preload_libraries TO 'pg_hint_plan';
 SET pg_hint_plan.enable_hint TO on;
 SET pg_hint_plan.debug_print TO on;
 SET client_min_messages TO LOG;
@@ -1424,10 +1423,3 @@ error hint:
                      Filter: ((id % 2) = 0)
 (28 rows)
 
-ALTER SYSTEM SET session_preload_libraries TO DEFAULT;
-SELECT pg_reload_conf();
- pg_reload_conf 
-----------------
- t
-(1 row)
-

sql/ut-G.sql

@@ -44,8 +44,6 @@ Set(enable_tidscan off)Set(enable_nestloop off)
 */
 EXPLAIN (COSTS false) UPDATE s1.r3_ SET c1 = c1 WHERE c1 = 1 AND ctid = '(1,1)';
 
-RESET client_min_messages;
-
 ----
 ---- No. G-2-1 GUC parameter
 ----

sql/ut-S.sql

@@ -1,12 +1,4 @@
 LOAD 'pg_hint_plan';
-
--- Force some GUCs.
-SELECT current_database() AS datname \gset
-ALTER DATABASE :"datname" SET client_min_messages = 'log';
-ALTER DATABASE :"datname" SET pg_hint_plan.debug_print = 'on';
-ALTER DATABASE :"datname" SET session_preload_libraries TO 'pg_hint_plan';
--- Force GUC reload with a reconnection
-\c
 SET pg_hint_plan.enable_hint TO on;
 SET pg_hint_plan.debug_print TO on;
 SET client_min_messages TO LOG;

sql/ut-W.sql

@@ -1,5 +1,4 @@
 LOAD 'pg_hint_plan';
-ALTER SYSTEM SET session_preload_libraries TO 'pg_hint_plan';
 SET pg_hint_plan.enable_hint TO on;
 SET pg_hint_plan.debug_print TO on;
 SET client_min_messages TO LOG;
@@ -233,6 +232,3 @@ SELECT id FROM ft1
  UNION ALL
 SELECT x FROM (VALUES (1), (2), (3)) t(x);
 ');
-
-ALTER SYSTEM SET session_preload_libraries TO DEFAULT;
-SELECT pg_reload_conf();