Port bisect wrapper to act-tester?

[MattWindsor91]

In act-bash, we have a set of bisection tools that are useful for lifting the tester into act-fuzz's bisector. There are a few issues with these, though:

• they're written in bash, which is quite hard to maintain;
• they don't have a particularly pleasant user experience;
• they don't have knowledge of act-tester's plan format, and so rely a lot on manual specification of things that can be gleaned from a plan file;
• the low-level runner could arguably benefit from being a single self-contained shot of the director, rather than a script tying together lots of other programs (this'd likely need measuring but I bet there's some overhead).

This issue tracks the possibility of:

• rewriting bisect-driver as a director invocation, likely by making it possible to change the fuzzer used by the director, cap the number of times it runs experiments, and strip away some of the chrome;
• rewriting bisect as a Go tool that takes a plan file and sets up the invocation of the driver from that plan file's information.

[MattWindsor91]

The FuzzRunner being implemented as part of the coverage testbed generator seems like it'd be a good place to start for making a 'lean' single-file runner, which would also be useful here (instead of using the full director).