Expand competitive benchmarks to track nonlocal performance changes

[countvajhula]

As we add nonlocal compiler optimizations (including e.g. deforestation, #77 ), we need some way to track that the optimizations are actually making a difference. Since these are nonlocal optimizations and not related to any specific form (alone), it would be nice to expand the suite of competitive benchmarks in profile/competitive.rkt that compare performance against Racket.

This way, we would see both progress against Qi's own past performance, but also gains against Racket. It'd be nice to even beat Racket performance once in a while 😉 . Given that we are able to assume "no accidental side-effects", which Racket cannot, this seems achievable.

Examples of benchmarks we could add include:

• those involving functional data transformations (map, filter and fold)
• (collect more here)