PHP-DI's test now uses a cache

Running PHP-DI without a cache don't make sense since PHP-DI parses annotations and uses the reflection.

On my machine I saw speed improvements of 2× for every tests, and much more for tests n°3.

Also, I think adding the number of required files to the benchmark is useless since it's an "internal" metric. It can affect speed or memory (or both) but that's it. So speed and memory are the only things that matter.

Also, the tests should be run with an opcode cache, like in a real production environment. This can affect PHP-DI's speed since, as you have seen, it includes many files.