[LVGL+Flow] Add support for display (in)activity in LVGL widget

[fietser28]

Is your feature request related to a problem? Please describe.
No a feature to make it easy to setup display timeouts like screensaver or go back to a main screen after some time of inactivity in flow without any native code.

Describe the solution you'd like
Add the following actions to the LVGL widget:

• Display Get Inactivity. This should return the value from lv_display_get_inactive_time()
• Display Trigger Activity. This should call lv_display_trigger_activity().
  AFAIK this is equal in V8 an V9.

Describe alternatives you've considered
Use simple native variable to get the inactivity timer and a simple native action to trigger activity.
OR
Implement manual timer and triggers In flow although this is not easy/nice to do.

Additional context
This came up in recent Discord question.