Built-in performance statistics
Add a performance monitor that would account for:

- Time spent in `_update` (or `_update60`)
- Time spent in `_draw`
- FPS
- Skipped frames (whatever the implementation should be here)
- XIP cache statistics
- Any sort of CPU performance counters
- Built-in profiling of things like `flip()`
- Implement a sampling profiler? Probably not feasible without being able to extract the final profile data; can wait