"Immediate navigation" option: Only make available if Google Maps is installed

[johan12345]

The "Immediate navigation" option switches the navigation button to use a special Intent that only works with the Google Maps app, but starts route guidance immediately instead of just showing the location on the map first.

On devices without Google Maps installed, this will not work. So we should check whether Google Maps is installed and if not, hide the option + always use the generic geo-intent.

[johan12345]

When clicking the navigation button, we already check whether Google Maps is installed and fall back to the generic intent otherwise. But still, we can hide the setting if it's not relevant because Google Maps is not installed.