Provide primary key values for data in tests that aren't about primary keys.

Provide primary key values for data in tests that aren't about primary keys.

(message written by Mike) some backends such as BigQuery have no
autoincrement mechanism at all.
while we would like to pursue a strategy where provisioning.py could
provide for an in-Python sequence generator, at least remove
the need for autoincrement in suite tests that don't need it.

Fixes: #6469
Closes: #6504
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/6504
Pull-request-sha: c075014ef7de33e6eb3f389d24251ba184655e0b

Change-Id: I98e237a38417b68c87d0201717205d7655b1f44e