Instead of having many small independent tests, we now just have a single test that pulls in all the individual tests and runs them together.
Concretely, each `.ql` file has been turned into a `.qll` file with a query predicate corresponding to the original `select` clause and named after the original `.ql` file, plus a prefix `test_`.
The newly added `tests.ql` imports all these `.qll`s.
The individual `.expected` files have been concatenated together into `tests.expected`, each prefixed with the name of the corresponding query predicate. (This is the format that qltest produces for tests with multiple query predicates.)
