remove old benchmarks, add new benchmark for #14394

[vkarpov15]

Summary

Currently the benchmarks dir is filled with old benchmarks that haven't been maintained since 2013. Given that we're looking to focus more on performance, we should remove the stale benchmarks and instead start building out a new benchmark suite based on benchmarks we've found useful, like #14394.

Here are some priorities for new benchmarks:

1. Minimal overhead: just a plain Node.js script. No frameworks like benchmark, because benchmark adds (admittedly minimal) overhead that adds extra noise to output from tools like 0x, which I now rely on heavily for perf debugging.
2. Includes setup code, but also allows skipping expensive setup using MONGOOSE_BENCHMARK_SKIP_SETUP environment variable. Also for flamegraphs, as well as faster iteration.
3. Outputs only a JSON object that contains timing info, which we can then later store in MongoDB. We used to store benchmark results for our TypeScript benchmark, we disabled that temporarily but I would like to get that going again. It would be wonderful to have a website like perf.mongoosejs.io or something similar that shows Mongoose's performance on benchmarks over time.

Examples

[hasezoey]

LGTM, though why is this PR targeting vkarpov15/gh-14394-2 (is it because it is build on it)?

[vkarpov15]

Yep exactly, we will merge this PR into #14623, and then merge #14263.