This introduces `reviewboard.reviews.testing.queries.reviews`, which provides the following functions for building expected queries and Q-expressions: * `get_reviews_accessible_q()` * `get_reviews_accessible_equeries()` * `get_reviews_from_user_q()` * `get_reviews_from_user_equeries()` This covers all the queries made in `ReviewManager`, giving us what we need for any unit tests that need to check accessible reviews. The `ReviewManager` unit tests have been updated to use these, simplifying that code considerably.