Benchmark sanitization and minor additions

[Izaakwltn]

Addressing issue #1204, this sanitizes the directory while we figure out how to replace trivial-benchmarks.

• Changes the benchmarks library to package-per-file
• Removes trivial-benchmarks as a dependency

This also adds two benchmarks from the Benchmarks Game, with hopeful additions coming soon.

I think next steps (for future PR(s)) should include a simple Coalton benchmarking framework, ideally without external dependencies, and incorporation of benchmarks into CI.

[Izaakwltn]

Whoops, I thought I marked it as a draft