db: Grant read access to guest user on all tables of the schema
This now automatically grant read-only access to the guest user at db initialization or upgrade time. This way, sysadm no longer have to manually alter the schema after initialization or upgrade.
Related to swh/infra/sysadm-environment#4228 (closed)
Test Plan
tox should still be happy
Migrated from D7913 (view on Phabricator)