This changes introduce a platform adaptation over ATT/GATT that can be implemented by porter.
Unlike the GattClient interface, the ATT/GATT adaptation is simple, follow closely the Bluetooth specification and won't change over time.
Implementation of the GattClient interface is realized by the class GenericGattClient which accept in input a pal::GattClient.
This change will also free design space once adopted by partners, addition to the GattClient interface won't require partner support.
Vincent Coubard