Android: Better implementation of on back button pressed

Currently it uses ```override fun onBackPressed()``` for handling on back pressed.

It is recommended to upgrade the handling of that.

https://developer.android.com/guide/navigation/custom-back

https://stackoverflow.com/questions/75462234/proper-usage-of-onbackpresseddispatcher

Best could be to keep the current way for older Android versions, and implement the newer version for newer Androids.