Initial event manager work, and two first events.

* Add initial event manager implementation,
  roughly mimicking Nordic's API.
* Add `position_state_changed` and
  `keycode_state_changed` events.
* Hook up HID and keymap to new events
  instead of using behaviour global event
  crazy.

app/Kconfig

@@ -73,6 +73,9 @@ config ZMK_ACTION_MOD_TAP
 	
 endmenu
 
+config HEAP_MEM_POOL_SIZE
+	default 200
+
 module = ZMK
 module-str = zmk
 source "subsys/logging/Kconfig.template.log_config"