psql: Add support for \dpS and \zS.

psql: Add support for \dpS and \zS.

This allows an optional "S" modifier to be added to \dp and \z, to
have them include system objects in the list.

Note that this also changes the behaviour of a bare \dp or \z without
the "S" modifier to include temp objects in the list, and exclude
information_schema objects, making them consistent with other psql
meta-commands.

Nathan Bossart, reviewed by Maxim Orlov.

Discussion: https://postgr.es/m/20221206193606.GB3078082@nathanxps13