pg_dump/pg_restore now always use SET SESSION AUTHORIZATION, not \connect,

pg_dump/pg_restore now always use SET SESSION AUTHORIZATION, not \connect,
to control object ownership.  The use-set-session-authorization and
no-reconnect switches are obsolete (still accepted on the command line,
but they don't do anything).  This is a precursor to fixing handling
of CREATE SCHEMA, which will be a separate commit.