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end was withdrawn due to issues with parallel runs.

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

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

@@ -91,3 +91,5 @@ 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;

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

@@ -106,3 +106,6 @@ 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;