Implement basic high level benchmarks to enable further optimization work.

[zleyyij]

There's a lot of low hanging fruit that can be done in terms of performance improvements.

• Decisions need to be made as to whether we want to use Criterion, or the native cargo-bench suite, currently only available on nightly (see Stabilize #[bench] and Bencher? rust-lang/rust#66287).
• Look into flamegraphs
• https://nnethercote.github.io/perf-book/profiling.html

[zleyyij]

It may also be prudent to add some sort of performance logging in production, we're pulling in the chrono crate.

[zleyyij]

Flamegraphs were added to the docs

[zleyyij]

More benchmarks added