inactivity: Use LVGL inactivity timers

Replace custom FreeRTOS inactivity timers with LVGL inactivity timers.

DisplayApp: Trigger display activity on timer done.

inactivity: Add additional checks
The backlight could be turned on by RestoreBrightness() on ble connect
event.

inactivity: Trigger activity on screen switch

A notification timing out could put the watch to sleep immediately.
While this could be ideal behaviour, it was caused by delay in
processing the EnableSleeping event and pushing RestoreBrightness to
DisplayApp.

src/displayapp/screens/settings/SettingDisplay.cpp

@@ -69,7 +69,6 @@ void SettingDisplay::UpdateSelected(lv_obj_t* object, lv_event_t event) {
       if (object == cbOption[i]) {
         lv_checkbox_set_checked(cbOption[i], true);
         settingsController.SetScreenTimeOut(options[i]);
-        app->PushMessage(Applications::Display::Messages::UpdateTimeOut);
       } else {
         lv_checkbox_set_checked(cbOption[i], false);
       }