Add timestamps to position and behavior events (#147)

* Add timestamps to position events and behaviors.

- Take original event timestamps into consideration so nested tap-holds have proper timing.
- Add position and timestamp to keycode state changed event so the one-shot behavior can properly identify other keypresses and timings.
- Add timestamp to position events received from peripheral

* reduce number of arguments to behaviors

app/src/kscan.c

@@ -52,6 +52,7 @@ void zmk_kscan_process_msgq(struct k_work *item) {
         pos_ev = new_position_state_changed();
         pos_ev->state = pressed;
         pos_ev->position = position;
+        pos_ev->timestamp = k_uptime_get();
         ZMK_EVENT_RAISE(pos_ev);
     }
 }