Remove Mapbox Geocoder

[boldtrn]

Motivation

We would like to remove dependencies on Mapbox.

Implementation

Right now the MapboxGeocoder is only used at one location, in the CarPlayManager. This code part if protected by:
#if canImport(MapboxGeocoder)

One quick fix would be to simply delete the Mapbox dependency from the Cartfile. Everyone using Carplay has to import the Geocoder though.

The better approach would be to remove the Geocoder call from the CarPlayManager and make it easy for implementers to create their own search implementation.

If anyone wants to give this a try, PRs are welcome :)