[API]: Unify Send API

[harlem88]

Currently each Astarte Device SDKs has a different name for the function that allows publishing data to an Astarte instance.

We want to unify the Send API across all SDKs to avoid confusion for the end user, who may use different SDKs for various use cases and could become disoriented.

All SDKs will implement the unified API for publishing data to an Astarte instance.

The API for publishing a property value already follows the unified API, we have to change only the datastream api:

Currently for both datastream interface (individual, object ) we use the streamData method, in the new API we moved to send :

public interface AstarteAggregateDataStreamer {
  void send(String path, Map<String, Object> payload)
      throws AstarteTransportException, AstarteInvalidValueException,
          AstarteInterfaceMappingNotFoundException;

  void send(String path, Map<String, Object> payload, DateTime timestamp)
      throws AstarteTransportException, AstarteInvalidValueException,
          AstarteInterfaceMappingNotFoundException;
}

...

public interface AstarteDataStreamer {
  void send(String path, Object payload)
      throws AstarteTransportException, AstarteInvalidValueException,
          AstarteInterfaceMappingNotFoundException;

  void send(String path, Object payload, DateTime timestamp)
      throws AstarteTransportException, AstarteInvalidValueException,
          AstarteInterfaceMappingNotFoundException;
}