Revive benchmark

[Leonidas-from-XIV]

Since we are not benchmarking against JSON Wheel anymore I took the liberty to remove the dependency and just port the previous benchmark into Core_bench which is very good at reporting performance numbers. Since this is not part of what people will need to use yojson or even run its tests I thought I'd prefer to just use an existing mature benchmark solution instead of rolling my own.

Maybe some more demanding benchmark data would be nice, and some more operations to test but for now I'll just await your input.

[Leonidas-from-XIV]

For the record, current values on the machine I'm developing on:

Estimated testing time 20s (2 benchmarks x 10s). Change using -quota SECS.
┌──────────────┬──────────┬───────────┬──────────┬──────────┬────────────┐
│ Name         │ Time/Run │   mWd/Run │ mjWd/Run │ Prom/Run │ Percentage │
├──────────────┼──────────┼───────────┼──────────┼──────────┼────────────┤
│ JSON reading │  18.23us │ 1_167.02w │    2.23w │    2.23w │    100.00% │
│ JSON writing │  10.45us │   721.00w │  258.30w │    0.30w │     57.33% │
└──────────────┴──────────┴───────────┴──────────┴──────────┴────────────┘

[NathanReb]

Thank you very much, this is a welcome change!

As you already said this is meant for developers so indeed using an external benchmark library isn't an issue at all here.

With time it might be interesting to add various type of input. Having a way to generate them so that we don't have to commit various and potentially large json files to the repo would probably be the way to go.

That's already great as it is and at least we have something to work with now!