This is a unit test helper method that can batch-create many review

requests at the same time. This is much faster than calling

create_review_request() in a loop, and performs as many operations in

batches as possible.
Not all state or operations can be set in this mode. For example, review

requests can't be published, though they can be set to be public. If

specific review requests need to have operations performed, they can be

called separately once created.
When marking review requests public, this will also take care to set the

counters on any review groups, reviewers, or the owner, as appropriate.

Made use of this in some upcoming unit tests that need lots of review

requests, and are sensitive to the counter fields.