Create a benchmarking test #122
Description
Benchmarking would be useful to check how it's performing on a device and as alongside #121 to help catch regressions. For example, a button in Settings to "run benchmark" which would do a test large-scale battle and measure average/5%/0.5%/min FPS through the battle. It would also be good to get accurate reproducible numbers for things like testing web for native performance, or just comparing devices.
Note: the benchmark battle would want a fixed randomness seed so it was always the same. Side note: this would be really useful anyway so a user could "save" and "load" battles and so reproducible them exactly eg for bug fixing.