CI: Adding a benchmark framework

[GuillaumeASSIER]

Hi,

As sozu need strong performances, we need a simple way to benchmark sozu regularly.

I create a complete sozu benchmark script using python who's in charge of booting a sozu with lagging_server, load certificates with a complete configuration and run a stressing tool. At the end, we collect all the results in a log file archive as an artifact.

It's automated with a CI called benchmark.yml to automate the build and the benchmarking tool. For now, I use bombardier, but we can easily add new testing tools.

This setup test sozu performances with following settings :

• 1 Minute duration
• 400 connections at max
• HTTP1 (HTTP2 can be support if needed)
• HTTP Plain text
  • HTTPS with the following encryption settings
  • RSA 2048
  • RSA 4096
  • ECDSA

The aim is not to get some reliable results, but to get a simple methodology that we can reuse in the future to track sozu performances.

[Keksoj]

I understand this is a clean rebase of #1042 Looks good to me!