Performance benchmark/check automation

[malaskowski]

Context
From time to time, we need to introduce changes, that impact all modules and probably Knot.x performance (e.g. upgrades to Java 11, Vert.x 4, bigger internal refactors etc.). We need a quick way to compare the performance before and after changes.

Describe the solution you'd like
I'd like to have ready to setup solution, where quick performance checks/benchmark can be executed. This is not idea to have full performance tests. This should be just a check, which can be followed by performance tests if necessary (e.g. there is worse result of the check after the change).

The check should include:

• Executing several scenarios and measuring response times, throughput and errors number.
• Scenarios should be diversified, including fragments processing (JSON Web API endpoint, as well as template engine variant), http server basic scenario (no fragments processing), ...

Solution should be easy to setup, monitoring is not required. If possible it should base on the Knot.x Starter-Kit and easy to update as the project evolves.