Support Location Override

Enable native location override to take incoming user locations and pass it through into mapbox. Trying to override the current experience using layers to mock a blue dot and shifting the camera to follow the blue dot feels inauthentic leading to a poor user experience.

Current limitation

• The Flutter SDK does not expose location.override(provider:) (iOS) or overrideLocationProvider (Android).
• FollowPuckViewportState follows Mapbox's internal GPS provider.

Desired behaviour

• Provide an API to override the location provider in Flutter.
• Allow injecting external location updates (lat, lon, accuracy, heading) from Dart into the overridden provider.
• When overridden, Mapbox GPS should not be active
• FollowPuckViewportState should smoothly follow the injected locations, preserving the current UX.

Start by tracing the Flutter location API alongside the native location.override(provider:) and overrideLocationProvider entry points. Review how FollowPuckViewportState obtains location updates, then define the override lifecycle and verify that injected latitude, longitude, accuracy, and heading updates are followed without the Mapbox GPS provider remaining active.