Drop global objects after completed test

Project policy is to not leave global objects behind after a regress
test run.  This was found as a result of the development of a patch
to make pg_regress detect such leftovers automatically, which in the
end was withdrawn due to issues with parallel runs.

This was originally committed as 936e3fa378, but the issue also exists
in the 12~16 range.

Discussion: https://postgr.es/m/E1phvk7-000VAH-7k@gemulon.postgresql.org
Backpatch-through: 12

src/test/modules/test_pg_dump/expected/test_pg_dump.out

@@ -91,6 +91,8 @@ ALTER EXTENSION test_pg_dump DROP SERVER s0;
 ALTER EXTENSION test_pg_dump DROP TABLE test_pg_dump_t1;
 ALTER EXTENSION test_pg_dump DROP TYPE test_pg_dump_e1;
 ALTER EXTENSION test_pg_dump DROP VIEW test_pg_dump_v1;
+DROP OWNED BY regress_dump_test_role RESTRICT;
+DROP ROLE regress_dump_test_role;
 DROP EXTENSION test_pg_dump;
 -- shouldn't be anything left in pg_init_privs
 SELECT * FROM pg_init_privs WHERE privtype = 'e';

src/test/modules/test_pg_dump/sql/test_pg_dump.sql

@@ -107,6 +107,10 @@ ALTER EXTENSION test_pg_dump DROP TABLE test_pg_dump_t1;
 ALTER EXTENSION test_pg_dump DROP TYPE test_pg_dump_e1;
 ALTER EXTENSION test_pg_dump DROP VIEW test_pg_dump_v1;
 
+DROP OWNED BY regress_dump_test_role RESTRICT;
+
+DROP ROLE regress_dump_test_role;
+
 DROP EXTENSION test_pg_dump;
 
 -- shouldn't be anything left in pg_init_privs