Add multi-statement fuzzing

[Mytherin]

Currently the fuzzer script/reduction script only supports single-statement fuzzing, which works to detect problems/internal exceptions/memory safety issues in individual statements (e.g. SELECT ...).

Often problems are found as a combination of statements, however. For example, creating an index followed by running a select statement. To support this we will need to add support for multi-statement fuzzing where many statements are run and reductions will re-run multiple statements (and prune unnecessary statements for triggering the found issue).