Update benchmarks

[diegonehab]

Context

It has been a while since we benchmarked the emulator. We should keep these benchmarks up to date so we can check if we are introducing a performance regression.

Possible solutions

Add benchmarking to CI and publish the reports. Also flag any regression.

[edubart]

For those reading this issue, I have set up some benchmarks in the wiki at https://github.com/cartesi/machine-emulator/wiki/Benchmarks. However, this is currently done manually.

You can also benchmark the emulator yourself and try to reproduce these numbers using the stress-ng tool, which is now part of our standard rootfs image.