Remove test tables after a successful test completion

And add option to keep them. The conditional dropping can be done by creating a table with the test's result and then using a conditional on it.

```
IF EXISTS (SELECT 1 FROM test_result WHERE result)
BEGIN
-- drop the tables
END
```

No files, tests, or entry points are named. Start by locating the code that creates and removes test tables and the existing SQL-query test suite; trace how a test result is recorded, then verify both conditional cleanup and the option to retain tables after successful completion.

Written by the indexing model from the issue text.