anduril: party strobe pulses have inconsistent duty cycle

The party strobe mode uses very short pulses, and the duration of those pulses varies enough that it looks weird sometimes. This happens because it can only really turn on or off at the edge of a PWM cycle, but the control logic isn't synced to that cycle. So sometimes it'll be on for 4 cycles, sometimes 5. (or maybe 3 and 4, not sure) This makes some pulses significantly brighter than others.

This could be fixed by syncing to the PWM cycle, or it could be fixed by turning off PWM entirely and using the pins as binary outputs. I'm leaning more toward the former though, because it's more generic and less hardware-dependent. I expect the binary-output approach may become tricky as more types of power circuits are supported, since it would need code to handle each type individually.