Add a built-in benchmark tool

[dhh]

We should have a simple, built-in benchmark mechanism for people to evaluate different computing platforms. Whether they be cloud VMs, Raspberry Pis, or 96-core state-of-the-art owned server hardware. Think Geekbench or Speedometer. Run a big test suite, on a single machine, produce one comparable number. "Oh, that new box we got? It does 3,456 on the Rails Speedrun!!".

Easily comparable numbers make for better comparisons make for better buying decisions.

[nickjj]

I really like this, what do you envision the scope of this being?

For example:

• A clone'able demo app that Rails maintains which has all of these tests set up and ready to go where someone interested in comparing these numbers could clone the repo on a box and run a command to run the benchmarks?
• A new library within Rails that makes it easy to write custom performance tests and benchmarks for your custom app
• Something else?

The first option is interesting because it could be used to help create "real world'ish" performance regression tests for Rails itself.