Add performance tests around ensy

[adngdb]

Games need high performance, and as a center piece of games using it, the entity system must be critically fast and optimized. But it's a mistake to optimize blindly, so the first step is to collect metrics about the speed and memory usage of ensy, so that we can then find the bottlenecks and optimize them.

I'm very very noob in this domain so any recommendation or link is appreciated!