Benchmark for performance and memory usage

Issue fullstaq-labs/fullstaq-ruby-server-edition#7 described tuning additional settings for server-friendliness. I think that's a good idea, but one potential caveat is that we tune things wrongly. Of course it's impossible to tune things in a way that it's better for *all* workloads, but at the very least I think we should have some kind of performance and memory usage benchmark. However imperfect such a benchmark may be, having something is better than doing guesswork with no benchmark.

A standardized benchmark suite will also help us compare, when we implement new improvements (like https://github.com/fullstaq-labs/fullstaq-ruby-server-edition/issues/57), or when we research new memory allocators (like #4 and #6).

There are currently third party benchmark reports, but they are erratic and are hard to reproduce, so we can't rely on them.

How would such a benchmark look like? Can we reuse existing benchmarks or do we have to write a new one? Help on building or integrating a benchmark would be much appreciated.

The first goal is to have a benchmark suite. Once we have it, a second goal (which will be codified in a separate issue) is to integrate the benchmark in a CI and monitoring system (https://github.com/fullstaq-labs/fullstaq-ruby-server-edition/issues/58), so that we can automatically see the impact of changes over time.

No files, tests, or entry points are named in the issue. Start by reviewing the referenced server-friendliness, improvement, memory-allocator, and CI issues, then define a reproducible performance and memory benchmark suite; done means the suite exists and can compare changes over time.

Written by the indexing model from the issue text.