Allow pg_{read,write}_all_data to access large objects.

Allow pg_{read,write}_all_data to access large objects.

Since the initial goal of pg_read_all_data was to be able to run
pg_dump as a non-superuser without explicitly granting access to
every object, it follows that it should allow reading all large
objects.  For consistency, pg_write_all_data should allow writing
all large objects, too.

Author: Nitin Motiani <nitinmotiani@google.com>
Co-authored-by: Nathan Bossart <nathandbossart@gmail.com>
Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com>
Discussion: https://postgr.es/m/CAH5HC96dxAEvP78s1-JK_nDABH5c4w2MDfyx4vEWxBEfofGWsw%40mail.gmail.com