`Uart` is now an abstract class with a `UartEsp` and a `UartPosix` implementation.
- Fixes and improvements to `GpsSettings` app, `GpsDevice` and `GpsService` - Implemented location/GPS statusbar icon - Added app icon - Added support for other GPS models (based on Meshtastic code)
Also changed usage from unique_ptr to class value.
Implemented basic GPS support: - GPS HAL - GPS Service - GPS Settings app
