Improve psql's \d output for TOAST tables.

Add the name of the owning table to the footers for a TOAST table.
Also, show all the same footers as for a regular table (in practice,
this adds the index and perhaps the tablespace and access method).

Justin Pryzby, reviewed by Fabien Coelho

Discussion: https://postgr.es/m/20190422154902.GH14223@telsasoft.com

src/test/regress/sql/psql.sql

@@ -1131,3 +1131,6 @@ set search_path to default;
 
 set role to default;
 drop role regress_partitioning_role;
+
+-- \d on toast table (use pg_statistic's toast table, which has a known name)
+\d pg_toast.pg_toast_2619