Tests `util` and `repair` both used the same user name, so when
executing in the same parallel suite they could cause conflict.
Instead, use different role names for different tests.
If users have accidentally been removed from `pg_authid` as a result of
bugs where dropping a user did not revoke privileges from all tables
where the had privileges, it will not be possible to create new chunks
since these require the user to be found when copying the privileges
for the parent table (either compressed hypertable or normal
hypertable).
To fix the situation, we repair the `pg_class` table when updating the
extension by modifying the `relacl` for relations and remove any user
that do not have an entry in `pg_authid`.
A repair function `_timescaledb_functions.repair_relation_acls` is
added that will perform the job. A `makeaclitem` from PG16 that accepts
a list of comma and used as part of the repair is also added as
`_timescaledb_functions.makeaclitem`.
