psql \dX: check schema when listing statistics objects

psql \dX: check schema when listing statistics objects

Commit ad600bba04 added psql command \dX listing extended statistics
objects, but it failed to consider search_path when selecting the
elements so some of the returned elements might be invisible.

The visibility was already considered for tab completion (added by
commit d99d58cdc8), so adding it to the query is fairly simple.

Reported and fix by Justin Pryzby, regression tests by me. Backpatch
to PostgreSQL 14, where \dX was introduced.

Batchpatch-through: 14
Author: Justin Pryzby
Reviewed-by: Tatsuro Yamada
Discussion: https://postgr.es/m/c027a541-5856-75a5-0868-341301e1624b%40nttcom.co.jp_1